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Book L_fe___ 



6go 



PRINCIPLES 



OP 



CHEMISTEY 

EMBRACING THE MOST 

RECENT DISCOVERIES IN THE SCIENCE, 

AND THE OUTLINES 

OF 'iTS APPLICATION TO AGRICULTURE AND THE AR 




ILLUSTRATED BY NUMEROUS EXPERIMENTS, 

MEWLY ADAPTED TO THE SIMPLEST APPARATUS. 

BY JOHN A. PORTEB, M.A.,M.D., 

„™b OF AOBICO^BAE a™ OB»A*K, CEMXSTBV » YAU. OOOW 



NEW YORK: 

PUBLISHED BY A. S. BARNES & BURR 

51 & 53 JOHN STEEET. 

SOL P BV BOOTHS, 8 «UUT, THBOCOHOCX XHB *«- ST— 

18 60. 



$>4 

PORTER'S SCHOOL CHEMISTRY. 

PUBLISHED BY % \ 

A..S. BABXES & CO., 51 & 53 JOIffl-STBEET, K.Y. X% 



FIRST BOOK OF CHEMISTRY, AND ALLIED SCIENCES, 
In clad I tig an outline of Agricultural Chemistry. By Prof. John A. Porter. 50 cts. 

PRINCIPLES OF CHEMISTRY, embracing the most recent discoveries 
In the Science, and the outlines of its application to Agriculture and the Arts — 
illustrated by numerous experiments newly adapted to the simplest apparatus. By 
John A. Porter, A. M., M. D., Professor of Agriculture and Organic Chemistry in 
Yale College. Price $1. 

[A Box of Apparatus, prepared expressly for this Work, will cost $8 00.] 



From Prof. J. Young, of the JForth Western Christian University. 

" It does not give a mere outline, but exhibits the atomic proportions in all combina- 
tions so as to make the student scientific in his processes. It is fully up with the pro- 
gress of the age in this most rapidly advancing science ; and last, not least, in its behalf, 
it is so simple, easy, and beautiful, that a teacher can make himself a chemist while 
teaching a class." 

" Monroe, Butler Co., Ohio, Oct. 1, 1857. 

"I put a class into it last winter, which nearly finished it. I think I never used a 
text-book on any subject that pleased me so well. It seems just what our academies 
require. The clearness and simplicity of the explanations of principles are beyond all 
praise, and are unequaled in any work I have seen. The number and adaptation of the 
experiments, and the cheapness of the apparatus required, admirably fit the work for 
general use ; and lastly, the beauty of the mechanical part, and the good judgment of 
the whole arrangement, are worthy of all the rest. M. Sturges." 

"Frankfort, Kentucky, Feb. 15, 1858. 
" As an elementary Text-book, it is a model. I am at a loss which most to admire — 
the clear enunciation of the truths of the science, his happy arrangement of them, or 
the ingenuity he has displayed in placing so large a number of chemical manipulations 
within the reach of the humblest student. The book must greatly extend the study of 
this important science. , E. A. Grant." 

From M. L. Morse, Principal of High School, Dover, J\T. R. 
" I do not hesitate to pronounce it a work most admirably adapted to convey to any 
inquiring mind a clear idea of the elements of chemistry. The author has chosen the 
simplest, and, therefore, for beginners, the best means of investigation, requiring for 
apparatus only a few test tubes, pipes, glass bottles, corks, and a spirit lamp ; and for 
chemicals, a list of salts, acids, and metals, given on the last page, the cost of which is 
set at the extremely small sum of eight dollars." 

From the Massachusetts Teacher. 

" We have read this book with great pleasure, and can recommend it as the simplest, 
most concise, and most comprehensive School Chemistry known to us. Its simplicity 
is it* great merit. It disembarrasses the science of details unsuitable for beginners, 
states principles plainly and clearly, and by its admirable conciseness is enabled to em- 
brace in a single volume a complete outline of the great modern science, in its organic 
and inorganic departments." 

"Jersey Shore, Pa., Oct. 2, 1857. 

" Porter's First Book of Chemistry I have examined with very great satisfaction, and 
regard it as a most complete, simple, and yet every way admirable compendium of the 
science for beginners. The larger work I have adopted as a text-book, and I find its 
logical arrangement and lucid explanations very acceptable to my pupils, and admirably 
calculated to make them thoroughly acquainted with the important and interesting 
facts of chemical science. Yours, respectfully, W.W.Howard." 



Entered according to Act of Congress, in the year 1856, 

By JOHN A. PORTER, 

In the Clerk's Office of the District Court for the District of Connecticut. 



PEEFACE. 



In the preparation of this text-book on Chemistry, it has 
been the design of the author to disencumber the subject 
of much detail, which is only of interest to the professional 
chemist, and at the same time to bring the illustration of the 
more important phenomena of the science within the reach 
of every school and every individual student. 

The most distinguished philosophers have not deemed it 
beneath their dignity to employ the simplest means of inves- 
tigation. The teacher will not be loth to take advantage of 
similar means in illustrating their discoveries. An important 
design of this work is to show how this object may be ac- 
complished, by the simple addition of a few test-tubes and a 
spirit lamp, to a list of chemical apparatus which may be 
found in every house. 

Among the other distinctive features of the work, are a 
more complete classification than usual according to chemi- 
cal analogies, the explanation of chemical phenomena in 
ordinary language, as well as symbols, and the addition of 
a complete set of formulae in the Appendix. A number of 
recent and important discoveries are introduced, and the 
relations of Chemistry to the Arts and Agriculture, are es- 
pecially considered. 

The method adopted for the explanation of chemical phe- 
nomena, while it is believed to be more effectual in imparting 
the leading idea of all chemical reactions, leaves to the 

1 



ll PREFACE. 

student the useful exercise of constructing formulae. He 
is at the same time supplied in the Appendix with a com- 
plete control of his results. This part of the work contains 
in addition, numerous tables, and other supplementary mat- 
ter for the use of the more advanced student. The learner 
should not be required to burden his memory with numbers, 
expressing atomic weights, specific gravities, &c. It is a 
barren knowledge. A general survey of the tables, with 
reference to them for calculations, is sufficient. 

The language of the atomic theory has been rigorously 
adhered to throughout the work, as the best expression 
of our present knowledge of the constitution of matter. 
While it is liable to no objection which does not hold against 
the language of every department of Physics, its uniform 
employment has the great advantage of accustoming the mind 
to a conception which furnishes a probable explanation of the 
most obscure portions of the science. 

Several topics introduced in the chapters on Physics, are 
designed simply as introductory to other subjects, and are 
very briefly treated, in accordance with this design. 

Among the numerous authorities consulted in the prepa- 
ration of this work, the author would especially mention the 
works of Berzelius, Liebig, Gmelin, Gregory, Regnault, 
Payen, Graham, Silliman and Stockhardt. He would also 
take this opportunity of acknowledging the important aid 
extended by his able professional assistant, Dr. Robert A. 
Fisher, both in the execution of his design for a simplified 
course of experiment, and for valuable information in rela- 
tion to several processes of applied chemistry. 

Boxes containing apparatus and materials neatly put up to accom- 
pany this work, may be ordered of the publishers, A. S. Barnes & Co., 
61 and 53 John street, New York. Price $8.00. 

The list embraces all the articles named on the last page of the work, 
with the exception of those marked with an asterisk, which may be pro- 
cured of any druggist* 



TABLE OF CONTENTS. 



PART I. 

PHYSICS. 



PAGE 

Atoms and Attraction, ... 11 
Light. — Chemical action of 

Light, 15 

Theories, 15 

Laws, 17 

Analysis of Light, . . 22 

Heat. — Nature and Sources, 25 

Communication of Heat, 30 

Changes effected by Heat, 48 



PAGB 

Heat. — Expansion, ... 60 
Liquefaction, .... 61 
Vaporization, .... 66 
Boiling, 77 

Electricity and Magnetism, . 99 

Galvanism, 103 

Batteries, 114 

Galvanic Decomposition, 117 
Magnetic Telegraph, . .124 



PART II. 



CHEMICAL PHILOSOPHY. 



Number of Elements, . 
Atomic Constitution, . . 
Explanation of Symbols, 
Laws of Combination, . . 



7AGE 

. 129 
129 
132 

134 



PAGE 

Properties of Acids and Bases, 137 
Effect of Solution, . . . 138 
Electrical Condition of the 

Elements, ..... 138 



IV 



CONTENTS. 



PART III. 

INORGANIC CHEMISTRY. 



PAGE 

Metalloids. 

Oxygen, 141 

149 
156 
158 
158 
159 
169 
176 
179 
185 
197 
231 
233 
237 



Chlorine, 
Iodine, . . 
Bromine, . 
Fluorine, 
Sulphur, . 
Nitrogen, 
Phosphorus, 
Arsenic, . . 
Carbon, 

Boron, .... 
Metals. — Classification, 

Class I. — Potassium, <fcc. 
Class IL — Barium, &c. 



Metals. 

Class III.— Iron, &c. . 240 
Class IV.— Tin, &c. . 243 
Class V.— Bismuth, &c. 259 
Class YI. — Mercury, <fec. 258 
Solution and Crystalization, 274 
Precipitation, .... 275 
Variety of Crystals, . 279 
Forms of Crystals, . . 280 
Isomorphism, . . . .284 

Oxides, 285 

Chlorides, 294 

Salts, 300 

The Daguerreotype, . . .327 
Chemical Analysis, . . .332 



PART IV. 



ORGANIC CHEMISTRY. 



^vwvwwvwwvwvwwvi 



PAGE 

General Views 335 

Vegetable Chemistry, . . 345 

Wood, 349 

Starch, 357 

Sugar, 359 

Alcohol, 362 

Organic Acids, . . 372 

Essential Oils, . . . 379 
Artificial Essences, . .382 
Resins, 383 



page 
Vegetable Chemistry. 

Protein Bodies, . , . .388 
Organic Bases, . . . 395 
Coloring Matters, . . .396 

Dyeing, 397 

Calico Printing, . . . 400 
Agricultural Chemistry, . 402 
Animal Chemistry, . . . .412 
Organic Analysis, .... 429 
Circulation of Matter, . 431 



INTRODUCTION. 



According to the most ancient view of the constitu- 
tion of matter, the earth and all material things are but 
modifications of one and the same original substance. 
Fire, water, and air, were each in turn asserted to be 
the primitive element, according to the arbitrary con- 
jecture of philosophers who were bold enough to spec- 
ulate upon the subject. At a later date, the views of 
all seemed to be harmonized in ascribing the same 
dignity to the three contending elements, and including 
earth among the original varieties of matter. Earth, 
Air, Fire, and Water, were assumed to be the original 
materials out of which all forms of matter are produced. 

Modern chemistry has dethroned each of these ele- 
mental monarchs of the world, and distributed their 
prerogatives among a larger number. Earth, air, and 
water, are all excluded from the list of elements, and 



O INTRODUCTION. 

fire appears in the modern view as only the transient 
attendant of chemical combination. 

Each one of the acknowledged elements has its own 
specific properties, affinities, and capacity of combina- 
tion. These peculiaiities, and all resulting phenomena, 
it is the province of chemistry to investigate and ex- 
plain. Light, heat, and electricity, stand in intimate 
relation to all chemical action, either as cause or effect, 
or unfailing attendant, and are therefore briefly consid- 
ered in the earlier part of the present work. 

The study of science has not for its object the mere 
gratification of an idle curiosity. Looking at the sub- 
ject from a material point of view alone, chemistry is 
one of the great agents in the transformation of nature, 
and its subjugation to the wants of man. The earth 
yields her treasure to its skillfully conducted processes, 
and even the trodden clay becomes converted in its 
crucible into shining metal. The arts draw from it, 
with every succeeding year, increased advantage, and 
the condition of mankind is elevated, and the world 
advanced by its progressive triumphs. Agriculture 
also is indebted to its discoveries. It opens to us mines 
of agricultural wealth in what would otherwise have 
passed for worthless refuse. It clothes exhausted fields 
with new fertility, by the addition of some failing con- 
stituent whose absence its subtle processes have de- 
tected. It carefully investigates the laws and condi- 



INTRODUCTION. / 

tions of vegetable growth, by which earth and air are 
converted into food for man and beast, and thus places 
us on the highway of sure and rapid improvement. 

These practical results, which are the basis of that 
material prosperity in which taste, and literature, and 
the graces of life find their natural growth, are by no 
means to be disregarded. But this is not all. The 
study of chemical science reveals to the mind a beauty 
and harmony in the material world, to which the unin- 
structed eye is blind. It shows us all of the kingdoms 
of nature contributing to the growth of the tiniest plant, 
and feeding the germ, as it were, by the inter-revolution 
of their separate spheres. It shows us how through 
fire, or analogous decay, all forms of life are returned 
again to the kingdoms of nature, from which they were 
derived. Without encroaching upon the domains of 
the astronomer, it reveals to us still more wonderful 
relations of distant orbs, which affect not only the out- 
ward sense, but supply the very forces which we em- 
ploy in our contest with the powers of nature. It un- 
veils to us a thousand mysteries of cloud and rain, of 
frost and dew, of growth and decay, and unfolds the 
operation of those silent yet irresistible forces which 
are the life of the world we inhabit. 

But the study of nature is worthy of being pursued 
with a still nobler aim. The glory of the Deity shines 
in every crystal and blooms in every flower. Every 



s 



INTRODUCTION. 



atom is instinct with a life which the Creator has im- 
parted. The laws that govern minutest particles, as 
well as the grander revolutions of the heavenly spheres, 
are but the expression of His will. The reverent study 
of nature is therefore a contemplation of Deity. Vague 
and unsatisfactory without the aid of another, and 
written revelation, it unfolds to the mind thus enlight- 
ened, new and exalting evidences of the infinite wis* 
dom and beneficence of the Creator of the world. 



INTRODUCTORY. 



Whatdoescixe. L The g c i ence f Chemistry is of the 

vustry tell us J 

of Earth, Air, widest range. Air, Earth, Fire, and 

Fire, and Wa- Water? aR be]ong tQ itg domain . 

It informs us of the composition of the rocks which 
make up the mass of the Earth, and of the soil 
which forms its surface. It tells us of what Air is 
made, and how it supplies the wants of animal and 
vegetable life. It separates Water into gases, and re- 
produces it again by uniting them. It informs us of 
the nature of Fire, and of the changes which take 
place in combustion. 

2. It tells us of what plants are formed, 

What of met- r ' 

als,pla?its,a?id and what becomes of them when they 
decay and disappear. It tells us how to 
produce metals from ores, wines from fruit, liquors 
from grain, and shows us the changes which take place 
in the formation of all these substances. Almost all 
transformations which occur in the materials around 
us, as, for example, of iron into rust, of wood or coal 
into gas, of food into flesh, it belongs to Chemistry to 
describe and explain. 

i* 



10 INTRODUCTORY. 

3. As all of these changes result from 

\\ ky does it . . u 

treat of at- the action of the minute particles of mat- 
oms - ter on each other, it is necessary first to 

consider the subject of Atoms. 
Why of heat 4. As the mostof them depend on changes 

and light? . * 

of temperature, it is necessary in the first 
part of the work to consider the laws and effects of 
Heat. As these laws are best understood from their 
analogy to the laws of Light, and as Light has an import- 
ant influence in many chemical processes, a brief chapter 
on Light precedes the chapter on Heat and its vajvms 
effects. 

5. As many, and perhaps all chemical 

Why is elec- _ J r . l . , . . . 

tricity intra- changes, are accompanied by electrical 
ducedf phenomena, it is also important to dwell 

briefly on the subject of Electricity before proceeding 
to what is more strictly the science of Chemistry 
The first part of this work is, therefore, devoted to th* 
consideration of these subjects ; or, in other words, t < 
the Science of Physics. 



PAET I.-PHY8IOS. 



CHAPTER I. 

ATOMS AND ATTRACTION. 

* 

Of what is ■"•• A 701 " 18 - — All matter is supposed to be 

matter compo- composed of exceedingly minute spherical 

ted? What r & J r 

is said of or spheroidal particles, which are held to- 

atoms ? gether by their mutual attraction, and are 

never themselves subdivided. These particles are com- 
monly called atoms. There is reason to believe that 
the atoms of different substances differ from each other 
in weight and perhaps in size. The belief that they 
are never subdivided is not based on their extreme 
minuteness, but on other, grounds, to be mentioned 
hereafter. 

2. Minuteness of atoms.— Their mi- 

Eow is the mi- . 

nutenessofat- nuteness is shown by the fact that a sin- 

oms shown? gJe grain q{ mugk ^j fiU ft r0Qm w ^ 

its fragrant particles for years, without suffering any 
considerable loss of weight. The number of atoms it 
gives off during that time is beyond computation. 

4. Elements. — There are at least sixty 

Define and il- . . \ u ' 

lustrate an ele- different kinds of matter. Each kind which 
ment cannot be separated into other kinds is called 

an elementary substance, or simply an element. Iron 



12 ATOMS. 

and carbon or charcoal are elements. Iron rust, on the 
other hand, is a compound. There are, of course, as 
many different kinds of atoms as there are of elements. 

5. Cohesion. — The force which binds 

WhatisCohe- . . 

sion? lllus- together atoms of the same kind is called 
trate the sub- ^ attraction of cohesion, or simply co- 

ject. 

hesion. In the more tenacious substances, 
such as iron or copper, the force of cohesion is im- 
mense. The strength of a horse is insufficient, for ex- 
ample, to break an iron wire one-fourth of an inch in 
thickness. It is because in every section of the wire 
the atoms attract each other with a superior force. And, 
as we may imagine innumerable sections in every inch 
of the wire, we see that there is in every inch a force 
of attraction exerted, which in its sum total is inconve- 
niently great. Attraction between unlike atoms in 
contact with each other, as between glue and the wood 
to which it is applied, is called adhesion. 

6. Gravitation. — Unlike the force of 
vitationactT ^traction mentioned in the preceding para- 
graph, gravitation acts at all distances. It 

is the reason of the weight of bodies, one body weigh- 
ing twice or three times as much as another, because it 
has twice or three times the quantity of matter to at- 
tract and be attracted by the earth. 

7. Chemical attraction or affinity. 

What is Che- mi ,, .... ... 

mical Attrac- The force which unites unlike atoms into 
tion or Affim- compounds possessing new properties is 
called chemical attraction or affinity. Thus 
iron and oxygen unite by chemical attraction to form 
iron rust, a substance different from either. The 



ATOMS. 13 

gas chlorine and the metal sodium unite, as will be 
hereafter seen, to form common salt. When substances 
become thus united by chemical affinity, the resulting 
compound is not a mere mixture, with properties of 
both constituents, as when salt and sugar are mixed , 
it is, on the contrary, a new substance with properties 
of its own. 

8. Distance of attraction. — The forces 

Do the forces n . . , . . , 

of Cohesion of attraction above mentioned, with the ex- 
and Chemical ception of gravitation, act only at immeasu- 

Affinity act at r D J 

great distan- rably small distances. Two plates of glass 
an inch apart do not attract each other ; even 
when brought into absolute contact they do not ad- 
here. But if powerfully pressed, the atoms are brought 
within the range of the force of cohesion, and cannot 
again be separated. So iron and oxygen will not attract 
each other from a distance, but when brought together, 
unite in consequence of their chemical attraction. 

9. The three kinds of attraction are per- 

lllustrate the x 

three different fectly illustrated in a falling drop of water. 
kinds of At- Affinity holds together the atoms of oxy- 

traction. . 

gen and hydrogen which make up each 
particle of water. Cohesion unites the particles of wa- 
ter thus formed, to make the drop, and gravitation 
causes the coherent drop to fall. 
, Tr , M - x 10. Three states of matter. — There 

W hat are the 

three states of are three distinct states or conditions of 
matter. — the solid, the liquid, and the gas- 
eous. Almost all substances may be made to assume 
each of these states. Thus, a piece of solid sulphur, 
if heated up to a oertain point, melts and becomes 



14 ATOMS. 

liquid. If the liquid sulphur be exposed to a still higher 

temperature, it passes off in the form of a vapor or gas. 

11. Contact of atoms. — The atoms 

Are atoms in f ma tter are not supposed to be in ab- 

contact $ 

What is the solute contact in either solids, liquids, 

3£«£ * or § ases - This is inferred from . the fact 

cohesion in bo- that all substances maybe diminished in 
bulk by pressure. But in solid bodies the 
attraction of cohesion between the atoms is strongest, 
and they are more nearly and firmly bound together. 
In liquids, cohesion is less than in solids, and the atoms 
are farther separated. In gases, cohesion is entirely 
overcome, and but for gravity, the atoms would sepa- 
rate themselves indefinitely. 

Heat is the main cause of this difference in cohesion. 
This subject will be more fully considered in the chap- 
ter on Heat or Caloric* 

* The subject of Crystallization belongs to Physics, and in a strictly 
scientific arrangement, would be considered in this place. The student 
will find the most accessible illustrations of this subject in the Salts, 
which are considered later in the work, and it has therefore been in- 
troduced in the chapter which treats of these compounds. It is to be 
borne in mind that what is there said of crystallization, relates to other 
compounds and to elementary substances, as well as to salts. 



LIGHT. 15 

CHAPTER IT. 

LIGHT* 
_ , 12. Chemical action of light. — Da- 

ln what cases 

does light act guerreotype pictures are produced by the 

chemically? chemical action f light> g light acts 

chemically in converting water and the carbonic acid 
of the air into vegetable matter. The action of light 
in these cases will be explained hereafter. The present 
chapter is devoted to the consideration of its nature and 
more important laws. 

13. Light is without weight. — While 
wefate? ltght ^ e e ^ ects °f light, and the laws according 

to which they take place are well under- 
stood, philosophers differ with respect to its nature. It 
is. however, agreed that light is imponderable, or without 
weight, this being inferred from the fact that an illu- 
mined object weighs no more than the same object 
when unillumined. 

14. Newton's theory. — Newton main- 

What is Xeic- . _ ... . n • i i • 

to?i y s theory? tamed that light is a fluid thinner or more 

How is the sen- g^Jg t ] ian a J r or an y gr aSj ^ llt composed 
Sat 1071 oj si a lit 

produced? like these of minute particles, constantly 
given off from the sun and all luminous objects. He 
supposed that it is this substance passing into the eye 
that produces the sensation of sight, as the fine particles 
of fragrant matter, passing off from flowers, produces 
the sensation of smell. 

* This chapter is designed solely as an introduction to the subject of 
Heat. The undulatory theory is therefore not particularly considered. 



16 LIGHT. 

15. Undulatoky theory. — Another 
What ts the view is that the fluid above described does 

other view of 

the nature of not pass from the sun and other luminous 
objects to the eye, but fills the space be- 
tween them and serves as a medium for producing the 
sensation of light, as the air does for producing sound. 
7JJ . . ,,. 16. When a bell is struck its vibrations 

Illustrate this 

view ? are communicated to the air, and so to the 

ear, producing the effect of sound. So, according to the 
view of light last mentioned, vibrations are caused by 
some means in the sun and certain other bodies, which 
being rapidly transmitted through the fluid above men- 
tioned, produce, when they fall on the eye, the sensa- 
tion of light. 

17. Existence of the supposed fluid. 

How is this . . . 

fluid known to Such a fluid as this theory requires is known 
to exist in the spaces between the heav- 
enly bodies, by the influence which it exerts on their 
motions, and is supposed to pervade all substances, whe- 
ther solid, liquid or gaseous, occupying the spaces be- 
tween their particles. It is called ether, but has no re- 
lation to the chemical and medicinal liquid of the same 
name. 

18. For the explanation of the leading 
ther view el'- phenomena of light, it matters little which 

plain rcfiec- f the views above mentioned is adopted. 
Hon? . . . _. . . 

Thus, it is certainly true that light is re- 
flected from mirrors, whether we suppose it a subtle 
fluid, and that its reflection is the glancing off of its 
particles from the polished surface, (as a ball thrown 
obliquely against the side of a house glances off from 



LIGHT. 17 

it,) or whether we suppose it to consist of vibrations, 
which are made to glance off as the vibrations of the 
air in the case of echoes. 

19. The first, or Newtonian theory, ena- 
advantall of ^ es us to explain the leading facts more 
the Newtonian simply and clearly, and is therefore em- 

theory ? . 

ployed in this work for this purpose. The 
definitions and laws of light are stated in the language 
of that theory. 

Whatisaray 20. RaY AND MEDIUM DEFINED. A ray 

°/ l t 19 ^ 1 ' j}~ of light is a line of particles of light. In 
subject. such rays or lines of particles, light is con- 

stantly passing off from all visible objects. From every 
part of the book before the student, for example, it 
passes into the eye, enabling him to know the nature 
of the object. If the book is taken into a dark room 
it is no longer visible, because it obtains no light which 
it may afterward reflect to the eye. 
' 7 . . A medium is any space or substance 

What is a me- J r 

dium? through which light passes. 

/y . _. 7 21. Laws of light. — The more im- 

(Jive the Laws 

of light? portant laws of the radiation of light are 

the following : 

1. Rays of light proceed from ev- 
ery point of luminous objects in every 
direction. They proceed, for exam- 
ple, from every point of the sun's sur- 
face 

2. They proceed in straight lines. Light, for example, 
comes to us in straight lines from the sun. 

3. They diverge as they proceed. This is illustrated 





18 LIGHT. 

in the figure, the central point being supposed to be 
a star or other source of light. 
_ , , 22. Divergence of 

Explain the 

divergence of LIGHT. By the diver- 

rays of light. gence q{ rayg Qf Hght 

is meant that they spread them- 
selves over more space, the further they proceed from 
their source. This is illustrated in the figure, where 
the light of a candle is represented as passing through 
a window, and illumining a larger space on the opposite 
wall. 

23. Law of divergence. — When the dis- 

Givethelawof . 

divergence,and tance is doubled, the surface that light 

illustrations. w[l{ CQyer j g quadrupled . This ig alg0 

illustrated in the figure. The wall being twice as far 
from the candle as the window, the light covers four 
times the surface. If the distance of the wall were 
three times that of the window, the surface covered 
would be nine times as large as the window ; if four 
times, the surface covered would be sixteen times as 
large. It is evident from these figures that the surfaces 
covered, increase as the squares of the distances. The 
light, of course, diminishes in intensity in the same 
proportion, as it is thus spread over greater surface. At 
four times the distance, it has only one-sixteenth the 
intensity, and so on. 

24. Reflection of light. — If a ball of 

Explain the . . . 

reflection of ivory or other material is thrown perpen- 
hght. dicularly against any hard plane surface, it 

will r rt irn in the same line ; if it is thrown obliquely, 




LIGHT. 19 

it will glance off with the same degree of ob- 
liqueness in the other direction. Light is re- 
flected from plane surfaces in the same manner. 
This reflection is illustrated in the figure, 
which represents a mirror, and a ray of light 
falling upon it and again reflected. 

25. Apparent place changed by re- 
fhatigTof ^ flection. — As we always seem to see an 
parent place object in the direction from which its rays 

by reflection. . . _ . , 

enter the eye, a mirror which changes the 
direction of the rays will change the apparent place 
of the object. Thus, if the rays of the sun fall oblique- 
ly upon a mirror, and are reflected to the eye, we shall 
seem to see the sun in the mirror, in the direction 
which the rays have acquired after reflection. 

26. Concave mirrors. — 
c2 y tirZ's 0n considering that rays are 
converge rays reflected from plane surfaces 

of light ? . _ . _ „ : 

with the same degree of ob- 
liquity with which they fall upon them, ^^ ^U^ 
we shall be able to comprehend how it is 
that concave mirrors have the property of converging 
rays of light, or bringing them together in a point. 

A number of small plane mirrors, situated obliquely 
toward each other, as represented in the figure, and as 
they might be arranged in a bowl or saucer, would 
evidently have this effect. As a concave mirror may 
be regarded as made up of innumerable plane mirrors, 
similarly arranged, it would obviously be productive of 
the same effect. 



20 LIGHT. 

27. Refraction. — Re- 

jssit^" fracti °» is the chan § e ° f 

direction which a ray expe- 
riences in passing obliquely from a rarer 
into a denser medium, or the reverse. 

28. The figure represents a block of glass, 
foul™* the and shows ^e direction which a ray of 

light would take on entering and emerging 
from it. On entering, it makes a bend, and passes on 
through the glass less obliquely ; that is, more nearly in 
the direction of a line drawn perpendicularly to the sur- 
face of the glass, and continued through it. On passing 
out again it would be bent away from such an imagina- 
ry perpendicular line, and re-assume its previous course.' 

29. Another statement of the law. — 

Give another . 

statement of As the perpendicular has only an lmagina- 
*Re fraction °^ r ^ existence, it is perhaps easier to fix in 
the mind the changes of direction of rays 
passing in and out at regular surfaces thus : A ray, on 
entering a denser medium pursues within it a course fur- 
ther from the nearest portion of the surface than its origi- 
nal course would be if continued. And a ray entering a 
rarer medium takes a course nearer the nearest portion of 
the surface than its original course would be if continued. 
These statements are true for all plane or uniformly 
curved surfaces. 

30. Illustration. — A 
Illustrate by a QQm kced {r a tea _ cup as 

com. r r 7 

represented in the figure, 
so as to be barely concealed from the 
eye, will be rendered visible by filling the cup with water. 





LIGHT. 21 

The surface of the water furnishes a point of transi- 
tion from a denser to a rarer medium, and the direction 
of the ray is thereby changed in accordance with the 
law above stated. It is thereby enabled to turn a cor- 
ner, as it were, and come to the eye. 

31. Triangular prism. — Bearing the 

What effect . . a , . _ & 

has a prism 071 rules last given in mind, it will be readily 

way of light? see]Q that the CQmsQ of a fay of j ight pasg _ 

ing through a prism must be such as is 
represented in the figure. The ray may 
be supposed to start from below or above 
the prism. The line of its passage through 
the glass will be the same in either case. 

32. Let us suppose it to pass upward 

fjfat™* 6 tke ^ rom a k^ °f w hite paper or other object to 
the eye of an observer above. The appa- 
rent place of the object will be changed. It will be seen 
still beneath the prism, not where it actually is, but in 
the direction in which the ray points as it enters the 
eye. This experiment may be made equally well 
with the water prism described in the next paragraph. 

33. Construction of a Prism. 

How may a 

prism be con- The prism commonly used in 
optical experiments is of solid 
glass. In lack of this, its place may be rea- 
dily supplied by the water prism represented in the fig- 
ure. A strip of window glass is to be scratched with a 
file and broken frrto three pieces of equal length. These 
are set up, as represented in the figure, upon another bit 
of glass previously warmed and thickly covered with 
sealing wax. When the wax is cooled, and the bits 





22 LIGHT. 

of glass which it holds will stand alone, the comers 
where they meet are also closed with sealing wax. 
The prism is then filled with water, taking care not to 
moisten the upper edges, and a glass top is afterward 
attached by wax. 

34. Action of the 

Explain the LENS rjij^ propert y 

action of the A x * 

convex lens. which a convex lens pos- 
sesses of converging rays 
of light and heat, and bringing them 
together in a point, is also a consequence of refraction. 
All of the rays which fall upon its surface are bent, as 
shown in the case of the prism ; but, owing to its shape, 
they are bent in different degrees and directions, so that 
they all meet in a point. This point is intensely 
bright if brought on a dark object, and is called the 
focus. 

35. There is another law of refraction 
ther law of thus far left out of view, which is essen- 
refraction. t j al tQ a f ull un( j ers tanding of the convex 

lens. According to this law, the more obliquely a ray 
falls upon any surface the more it is refracted or bent out 
of its course. And it is a consequence of the shape of the 
lens, and its greater steepness toward the edge, that of 
all the parallel rays which fall upon its surface, those 
which fall furthest from the center fall most obliquely, 
and enter the air again more obliquely. In proportion, 
therefore, as they need to be bent to be brought to the 
focus, they are thus bent by the action of the lens. 

36. Analysis of light. — It has, up to 

mapped ^ this P° illt > been assumed that li £ ht is sim " 




LIGHT. 23 

pie in its nature, but it may be proved by experiment 
that every beam of white light such as we receive from 
the sun is made up of rays of different colors. 

37. This maybe done by holding a prism 

How is its . ' 

composition in the sun and al- 
P rGved ' lowing the light 

to pass through it and fall 
upon an opposite wall or ^ 
screen. A beautiful parti-colored spot will be produced, 
called the solar spectrum. The beam of light which 
enters the prism is separated by it into rays of seven dif- 
ferent colors. The experiment, if performed in a dark 
room, into which light is admitted through a very small 
opening, is extremely beautiful. 

38. The rays, before entering the prism, 

How does re- m " . 

fraction de- passing along together parallel with each 
ompose igi ot j ler? f orm w hjte light ; but on entering 
the glass and emerging from it, each of them is 
refracted or bent out of its course in a different degree, 
and they are thus separated, and made to appear with 
their own colors. Why one ray is refracted more than 
another is not known. The above experiment proves 
it to be a fact, and this is all our knowledge on the 
subject. 

Do lenses de- 39. LENSES DECOMPOSE WHITE LIGHT 

compose hght? AND RECO mbine the rays. — This separation 
of white light into colored rays occurs always when 
light passes through a prism ; but, for the sake of sim- 
plicity, this fact was left out of consideration in para- 
graph 29, the object in that place being simply to 
show the general direction of the light as it passes 



24 LIGHT. 

through the prism. Such separation also occurs when 
light passes through a lens, but the different colored 
rays on emerging again from different points of the 
lens overlap each other, and are in great part united 
again to form white light. 



NATURE OF HEAT. 2b 



CHAPTER III. 

HEAT. 

Section 1. — Nature and Sources of Heat. 
Has heat 40. Nature of heat. — It was remarked 

weight? Give . 

anillmtration in the commencement ot the chapter on 
light, that philosophers, although acquainted with its 
facts and laws, differed in opinion as to its nature. The 
same is true of heat. It is agreed, however, that heat, 
like light, is imponderable, or without appreciable 
weight ; this being known from the fact that a heated 
body weighs no more than a cold one. 

41. If the end of a bar of iron is heated, the 
other end soon becomes hot. There is no doubt 
as to the effect, and it would seem that something 
must have passed from the fire, along through the 
rod to produce it. But we do not certainly know 
that any substance has been thus transmitted. It may 
be that heat is analogous to sound, and produced by 
vibrations. Being thus in doubt, we say that the na- 
ture of heat is not understood. 

42. Mechanical theory. — One view is 

State the me- i i n • t r 

ehanical theo- that a very subtle fluid coming from the 
ry ' fire has actually passed along through the 

mass of metal, and from that into the hand, and so 
caused the sensation of warmth or Tieat. And this 
supposed substance is called heat, or caloric. 

2 



26 HEAT. 

What is the 43, Theory of Yibration. — Another 

theory of vi- 

bration * view, corresponding to the second view ot 

light, is, that heat is not a fluid, but, like light, the result 
of vibration in the ether which is every where present. 
The vibrations which produce the sensation of heat 
are, of course, different from those which produce that 
of light, as the movements of the air which produce 
heavy and sharp sounds are different. We must sup- 
pose, indeed, in the former case, that a much greater 
difference exists. But it is assumed that both are the 
result of vibrations of some kind. 

44. Illustration. — When a bell is struck 
Give the illus- - ts Orations are communicated to the air, 

tration. > 

and so to the ear, producing the effect of 
sound. So, according to this view, vibrations of a pe- 
culiar kind are caused by some means in the sun, and 
all sources of heat, and, being rapidly transmitted 
through the ether, produce, when they fall upon our 
bodies, the sensation of heat. The bar heated at 
one end becomes hot at the other, because certain vi- 
brations, originated in the fire, are gradually transmit- 
ted through the ether, and the iron which it pervades, 
to the other end. 

45. The facts are definitely known. 

What is the 

limit of our It may seem strange to the reader that 

fa^bnt? * there should be this doubt in elation to so 
common a subject as heat. But there is a 
similar limit to our knowledge in most of the sciences. 
In physiology, for example, we know that muscle, and 
bone, and other parts of the body, are produced from 
the blood, and that life, or vital force, is essential to 



SOURCES OF HEAT. 27 

their production ; but how the vital force operates we 
do not know. But, as in physiology this ignorance 
does not prevent us from comprehending the structure 
of the human body and the uses of its different organs, 
so ignorance in relation to the nature of heat does not 
interfere with the acquisition of the most perfect knowl- 
edge of its effects, and the laws according to which 
they happen. 

46. The mechanical theory here 
is ^dopteTln adopted. — In the present volume the for- 
thisicork? mer f the views which have been men- 

jbxplain it. 

tioned is adopted, and heat, like light, is 
assumed to be a.n exceedingly subtle imponderable fluid. 
To return to the example of the heated bar, it grows 
hot at the end farthest from the fire because the fluid 
actually passes through its solid substance, and is so 
communicated to the hand. 

47. Definition of cold. — Cold is a 

What is meant . . 

by the term relative term signifying the comparative 
absence of heat. But the coldest bodies 
which we know of, as ice, for example, contain heat, 
and may be made colder by its withdrawal. 

48. Sources of heat. — The principal 

State the pr in- 

cipal sources sources of heat are the sun and fixed stars, 
of heat, chemical action, electricity, and friction. 

It is by no means certain that these should be distin- 
guished as different sources ; for the heat of the sun 
may be due to chemical action, and electricity is, as 
we know, excited both by chemical action, and by 
friction, 



28 HEAT. 

Howmuchheat 49 # QUANTITY OF HEAT THE SUN SENDS 

does the sun 

send to the to the earth. — 1 he sun sends enough 
heat to the earth every year to melt a shell 
of ice enveloping the earth a hundred feet thick. This 
may be ascertained by observing what thickness the 
average heat of the sun will melt per minute, and then 
calculating the quantity for a year. The method ac- 
tually pursued is slightly different from this, but the 
same in principle. The sun, in fact, sends a larger 
amount of heat to the earth than is above stated, but 
40 per cent, of it is absorbed by the atmosphere. The 
quantity above given is the remaining 60 per cent. 

50. Total quantity of heat the sun 

Howmuchheat . 

is given out by gives out. — Knowing how much comes 

l atiZThe n feT t0 the earth an( * its atmos ph ere > it is easy 
to calculate how much starts from the sun. 
It is just in proportion to the extent of the whole visi- 
ble heavens, as seen from the sun, compared to the space 
occupied by the earth, as seen from the same point 
By making the calculation it is ascertained that a 
quantity of heat is given out from the sun in a year 
which, if it all came to the earth, would melt a crust 
of ice nearly 4000 miles thick, or a quantity which 
would melt every minute a crust nearly thirty-seven 
feet in thickness. But the heat of a blast-furnace, 
if kept up constantly to the highest point, would melt 
out a little over the thickness of five feet of ice per min- 
ute. The sun's surface is, therefore, more than seven 
times as hot as the glowing surface of the fire of a 
blast-furnace. 



SOURCES OF HEAT. 29 

What is said 51. HEAT OF THE FIXED STARS. The 

of the heat of .. ., _ 

fixed stars? fixed stars are suns of other systems, and 
sources of heat, like our own sun. And their number 
is so great, that notwithstanding their distance, they 
exert a very important effect on the temperature of 
the earth. It is estimated that they give us nearly as 
much heat as the sun, and that without this addition to 
the sun's heat, neither animal nor vegetable life could 
exist upon the earth. 

52. Heat of chemical action and 

Give examples 

of heat pro- electricity. — We shall see hereafter that 
duced by che- ^ eat j g evo i ve( j [ n almost all cases of che- 

mical action 

and by electri- mical action. Indeed, the heat of our fires 

citll. 

has this origin, as will be explained in an- 
other chapter. The heat of lightning is developed by 
electricity. 

Give examples 53. HEAT FROM FRICTION.— The heat 

of heat pro- p ro duced by slight rubbing is sufficient to 

duced by fric- r * i_ c% • 

tion. set on fire a phosphorus match. Sir 

Humphrey Davy produced heat by friction between 
two pieces of ice. It is said that Indians produce fire 
by rubbing two sticks of wood together. Count Rum- 
ford caused water to boil by boring a cannon beneath its 
surface. These are all cases of the production of heat 
by friction. 



30 



HEAT. 



Section 2. — Communication of Heat. 

54. Heat is communicated by conduction, convection, 
and radiation. These three modes of communication 
will be considered in the order in Avhich they are 
named. 

CONDUCTION. 

Explain the 55. Conduction is the passage of heat 

e ^ uctwn °f through a body by , communication from 

particle to particle. An iron wire, one 

end of which is held « > 

in aflame, soon grows Q 

hotter at the other, by conduction of the heat of the 
flame. The progress of heat along a wire may be 
shown by fastening marbles to it with wax, as rep- 
resented in the figure, and then heating one end by a 
lamp. The marbles drop off successively, as the heat 
in its progress melts one bit of wax after the other. 
The communication of heat from one body to another 
in contact with it is also a case of conduction. 

56. When conduction ceases. — Con- 

When does 

conduction duction proceeds toward the cooler por- 
tions of a body until all its particles be- 
come equally hot, just as the absorption of water by a 
sponge continues until all its pores are filled. This 
point being reached, there is no tendency to further 
motion within the heated body. 

57. The metals are the best con- 

WJtdt snt) ^fn,n~ 

ces are the best DucTcms. — The earths and wood conduct 
conductors/ V ery slowly ; fine fibrous suhstances, like 




CONDUCTION. 31 

wool, cotton, fur, and feathers, slowest of all. Liquids 
and gases, as will be hereafter seen, are non-conduct- 
ors of heat. The superior conducting power of metals 
is shown in the rapidity with which an iron wire, one 
end of which is held in the flame of a lamp, grows hot 
at the other end. A splinter of wood, or a pipe-stem, 
is heated from end to end much less rapidly, while 
scarcely any heat would be communicated along a roll 
of cotton cloth, one end of which was inflamed. 

58. Illustration. — The difference of 

How may the 

conducting conducting power in metals and earths may 
EZ&Z ^ illustrated by fastening 
lustrated? together by a wire, as repre- 
sented in the figure, an iron nail and a 
bit of pipe-stem of equal length, and 
heating them over a spirit lamp. The end of a match 
having been fastened with thread to each, it is found 
that the heat will travel along the nail and inflame 
the match at its end long before the other match is ig- 
nited. 

59. Protection from the central fire 

How are we 

protected from of the earth. — We are protected from the 

the central heat centml heat f the earth by the non -COn- 
of the earth ? J 

ducting power of the rocks and soil which 
form its outer crust. So a crust forms after a time over 
the streams of lava which flow from volcanoes ; but, 
owing to its non-conducting power, the lava below -re- 
mains liquid for years. 

60. Conduction from one body to an- 
St?ot° e * € tak6 other.— This takes place most rapidly 
place most ra- the more perfect the contact between the 

two. Conduction from air or a gas to a 



32 HEAT. 

solid is slow, because the gas contains comparatively 
few atoms, and therefore furnishes few points of con- 
tact. BetAveen a liquid and a solid it is more rapid, be- 
cause there are more. A cannon ball would grow hot 
much more rapidly in boiling water than in air of the 
same temperature. Between solid and solid, again, con- 
duction is less rapid, because the surfaces cannot 
<dapt themselves to each other, like liquid and solid, so 
*6 to bring all their atoms together. This paragraph 
refers solely to the passage of heat from the atoms of 
one surface into those of the other. The further con- 
duction of heat depends on the substance into which 
it has passed. 

61. Heating water. — Water is sooner 

Why is water . 

heated sooner heated in an iron pot, or other metallic 
l tfiMiin°a vessel, than in one of porcelain, glass, or 
glass vessel? earthen- ware, because the metal conducts 
the heat through from the fire more rapidly. Cooling, 
or the passage of heat outward when the vessel is re- 
moved from the fire, goes on more rapklly in the case 
of the metallic vessel for the same reason. These 
statements have reference only to vessels which are not 
polished. In the case of bright surfaces, another prin- 
ciple is involved to be considered hereafter. 

62. Clothing. — Fibrous substances, like 
subjcctZf do- wool; cotton, and furs, are best adapted for 
thing and its clothing because they are such poor con- 

r elation toheat. ° J ± 

ductors, and beside, because they contain 
air shut in between their fibres, which is a non-con- 
ductor, as will be hereafter shown. The object of 
clothing is not to impart heat, but to prevent its escape 



CONDUCTION. OO 

from the body. It escapes more or less through all 
substances, but less rapidly through the fibrous materi- 
als just mentioned, and therefore their superiority for 
winter clothing. If we lived in an atmosphere hotter 
than our bodies, the object of clothing would be to ex- 
clude heat, and the same non-conducting materials now 
used would be best adapted for this purpose also. 
Sometimes it is actually the object of clothing to keep 
out heat ; as, when workmen enter hot furnaces in cer- 
tain manufacturing processes. Thick clothing, of non- 
conducting materials, is obviously best in this case also. 
In summer, coarser fibre of linen, which is a better 
conductor than cotton or wool, is more used, because 
it conveys away the heat of the body more rapidly, as 
is desirable in the warmer season. 

63. Furs of animals. — We see, in 
Jjeity "varied what has been stated, the reason why the 
the covering of u e ity has clothed animals inhabiting cold 

animals ? J ° 

climates with fine furs. While the elephant 
of the torrid zone has but a few straggling hairs, the 
polar bear has a thick coat of fine fur to keep in his vi- 
tal heat, and enable him to endure the extreme rigor 
of a northern climate. So the sea-fowl has a thick 
covering of soft down to protect him from the cold of 
the ocean, while the ostrich has an open coat of scanty 
feathers. 
^ T1 , 64. Warmth of snow. — Snow keeps 

Why does snow . u 

tend to keep the earth warmer in winter than it would 

fe*£rt£5 oth erwise be, not because of any heat it 

imparts, but because, by reason of its low 

conducting power, and that of the air which it con- 

2* 



34 



HEAT. 



tains, it prevents the escape of the heat which is stored 
in the earth from the previous summer. But for this 
indirect warming effect of the snow, the cold of a sin- 
gle winter would be sufficient to kill whole races of 
plants. Thus, the cold of the winter weaves a garment 
to protect the earth from its own influence. 
How do the ^* Building. — I n building, the same 
principles of principles apply as in the case of clothing. 

conduction ap- ^ -. -, , . A , , , 

ply in the case ^ a( i conductors, when suitable in other 
of buildings? respects, are the best materials for walls, 
making a house cooler in summer and warmer in 
winter. Wood and brick, for example, are in this 
respect better than iron. They keep out the heat 
in summer, and, though they have the same effect 
to exclude the heat x>f the sun's rays in winter, they 
more than make up for this by preventing the escape 
of the larger quantity of heat produced by the fires in- 
side. The inhabitants of the Arctic regions build their 
winter huts of snow, and thus make practical use of 
its low conducting power. Double doors and windows 
have more than a double effect in preventing the escape 
of heat in winter, because of the non-conducting wall 
of air between them. 

66. Refrigerators 
walled wooden box- 
es, used to preserve 
articles of food from 
the heat of the summer. The 
space between the double walls 
and top is filled with pulverized 
charcoal, which has in itself very little conducting 



What is the 
principle in- 
volved in the 
construction of 
refrigerators $ 



-These are double- 




CONDUCTION. 



35 




power, and again is non-conducting because of the air 
between the particles. 

67. Fire-proof safes. — These are constructed on the 
same principle, the space be- 
tween the double walls being 
filled with gypsum, or some 
other non-conducting material. 
They are used as repositories 
of valuable papers and other 
property, for greater security in 
case of fire. 

How does con- 68. Sensation of heat. — A metallic 
auction ivflu- door . knob feels colder t han the wood to 

ence the se?isa- 

tionofheat? which it is fastened, although it cannot 
actually be so. It is because the metal is the best 
conductor, and carries off the heat of the hand more 
rapidly. If a piece of metal and wood be placed in a 
hot oven till both become equally hot, as they must 
by long exposure to the same heat, the metal will feel 
hotter than the wood. It is because the metal, by its 
greater conducting power, supplies heat more rapidly 
to its own surface to be taken away by the hand. 

Give a simple ^9. SlMPLE TEST OF CONDUCTING POWER. 

test for deter- As a general rule, the colder a body feels, 

mining the con- , , , . . 

ducting power the better conductor it is. That this is 
of a body. usually the case is evident from the last 

paragraph. On applying this test, we find the me- 
tallic lamp-stand, cooler, and therefore a better con- 
ductor than the table cover on which it stands. In 
an oven, or other place where the heat is greater than 
that of our bodies, the inference is reversed. For 



36 



HEAT. 



quids are non 
conductors ? 




the flow of heat would be in this case into the hand, 
from this highly heated object, and the body that 
brought it fastest, or felt hottest, would be thereby 
proved to be the best conductor. 

70. Liquids non-conductors. — Water 

How can it be 

proved that li- in a test-tube may be boiled at the top 
while ice frozen into the bottom will re- 
main unmelted. If a 

bar of metal with a cavity at the 

bottom for the ice were heated in 

the same way, the heat would be 

conducted downward so rapidly 

that the ice wou.d soon disappear. 

71. Fire on water. — Fire may be 
kindled on water by pouring a little ether 
upon its surface and inflaming 
it. But the flame will be found 
to have slight effect on the 

temperature of the water. And, what lit- 
tle effect it has, is principally due to the 
fact that the glass or metal of the containing vessel 
carries the heat downward and distributes it to the 
liquid. When water is heated by a fire beneath it, it 
is not by conduction, but by another process, explained 
in a subsequent paragraph. The above experiment 
may be made in a tin cup very nearly filled with water. 
A tea-spoonful of ether having been poured on the water, 
the bottle is to be corked and set away, for fear of ex- 
plosion, from the kindling of the ether which it con- 
tains. The experiment, as described, is not in the 
least degree dangerous. 



Explain the 
experiment 
with ether to 
prove that li- 
quids are non- 
conductors of 
heat. 




CONVECTION. 



37 



CONVECTION. 



„ - . , 72. It has been already shown that 

Explain how 

liquids become liquids and gases are non-conductors. 
This implies that they cannot be heated, 
like a mass of metal or other solid, by communi- 
cation of heat from particle to particle. Each parti- 
cle, on the contrary, receives its heat directly from the 
source of heat, and conveys it away, making room for 
others. Hence the term convection. In the process of 
boiling water, for example, the first effect of the fire is 
to heat the lower layer of liquid, and thereby to expand 
and make it lighter. It then rises as a cork would in 
water, and gives place to another portion, which be- 
comes heated and rises in its turn. Thus a circula- 
tion is commenced, the warmer portions ascending and 
the cooler descending, which continues until the water 
boils. Before this happens, each particle will have 
made many circuits, accumulating heat with each re- 
turn, but not communicating it to others. Air and 
gases become heated in the same way. 

73. Convection made visible. — The 
circulation above described may be ren- 
dered visible by adding a little of the " flow- 
ers of sulphur" to water, 
and then heating it in 
a test-tube over a spirit lamp. The 
suspended particles will be found 
to move in the direction indicated 
by the arrows, showing that the 
water has the same motion. The 



How can the 
circulation 
produced in 
liquids by heat 
be rendered r vis- 
ible ? 




38 HEAT. 

upward current is not, it is to be remembered, because 
of any tendency of heat to rise. Heat, on the con- 
trary, travels in one direction as well as another. 
But it is, -as before explained, because hot water is 
lighter than cold. Dust of bituminous coal answers 
the purpose in this experiment still better than " flowers 
of sulphur." It is necessary to have something that 
will neither sink or swim, but remain suspended in 
the water. 

74. Heating rooms. — A room becomes 

How does a . 

room become heated by a stove in the same manner. 
heated? The air in { mme ^ dite contact with the 

hot surface becomes heated and rises. Cooler air comes 
in from all sides to take its place, grows warm, and 
rises in turn. A circulation is thus established pre- 
cisely similar to that which occurs in the tube, as rep- 
resented in the figure. Any light object, as a feather, 
or a flock of cotton- wool, held over a stove or an open 
flame, will prove by its ascent the existence of the up- 
ward current. A smaller portion of heat is also com- 
municated by direct radiation, and by re-radiation, from 
the objects which first receive it. In the case of an 
open fire-place, this is the principal source of heat. 

75. Convection in the heating of the 

How is the at- . 

mosphereheat- atmosphere. — Heat is distributed through 
the earth's atmosphere in the same manner. 
At the equator, where the surface is hottest, the air 
heated by contact with it rises and flows off toward the 
poles, while colder air from the polar regions flows in 
to take its place, to be heated and rise in turn, contin- 
uing the circulation. But for this arrangement, the 



RADIATION. 39 

equatorial regions, which are constantly receiving ex- 
cess of heat from the sun, would soon become unin- 
habitable from its accumulation, and the polar regions, 
from extreme cold. The currents or winds thus pro- 
duced are subject to great irregularities, which are con- 
sidered in works on Natural Philosophy. 

f RADIATION. 

76. The general laws of radiation 

What art the - 

laws of the are the same tor heat as tor light. Kays 
™&™tion of f j ieat diverge constantly from all points 
of the surface of all bodies, in straight 
lines and in every direction ; and the intensity of heat 
varies inversely as the square of the distance. The 
latter point is explained in the chapter on light. 

77. Heat is radiated from all bodies. 

Illustrate the . . . 

fact that heat It is to be observed that while light pro- 
is always be- cee( j s on jy f rom certain bodies, heat pro- 

ing radiated J 7 r 

from bodies, ceeds from all points of all bodies without 
exception. If the mercury in a thermometer were fro- 
zen by extreme cold, and then hung in a cavity made 
for the purpose in a block of ice, radiation of heat from 
the ice would melt it, even if there were no air in the 
cavity to help melt it by conduction. 

78. Proportion of radiation to tem- 

TT hat can be 

mid of the pro- perature. — 1 he hotter a stove is the more 

portion of ra- heat it • eg QuL This j g b v i us. and We 

diatwn to tern- ° 

perature? might naturally suppose that a stove twice 

as hot as another stove, compared with other object' 
about it, would give out heat just twice as fast. It 



40 HEAT. 

gives out heat, in fact, more than twice as fast, the ra- 
pidity of radiation being more than in proportion to the 
temperature. 
TT77 , .. 79. Polish is unfavorable to radia- 

What are the 

effects of rough tion. — A coffee-pot of well brightened 
mrfacesonra- metal will keep its contents hot much bet- 
diatwn? ter t j ian a dingy, blackened one, thus re- 

warding the housewife for her pains, The brightness 
is not the cause of this effect. It is owing to the 
increased density of the outer surface which accompa- 
nies high polish. For it is satisfactorily proved by 
experiment, that by adding to the density of a surface, 
its radiating power is reduced, and vice versd. It is 
also generally found to be true, in the comparison of 
different substances, that radiating power is in some de- 
gree proportioned to density. Thus, lamp-black, paper, 
and cotton cloth, have high radiating power ; glass, 
plumbago, and shellac, less ; and the metals least of all. 
It is to be borne in mind, that it is the outer surface 
exclusively which influences radiation. Thus, a gilded 
globe of glass, radiates as poorly as solid metal, and 
the polished coffee-pot, used as a previous example, 
becomes a good radiator, and cools quickly, if covered 
over with paper or cotton cloth. 

80. Color does not affect radiation. — 

WJiat effect 

has color on A black coat wastes no more of the heat 
radiation? of the body by ra( jj at i 011 ^an a w hite one. 

Except in the direct rays of the sun, one is just as 
• warm as the other. But the former absorbs and imparts 



.REFLECTION. 41 

to the body more of the heat which comes to it asso- 
ciated with intense light, as 'is the case with the heat 
of the sun, and therefore its advantage as an article of 
winter clothing. 

What is said 81« Transmission. — The heat of the sun 
of the trans- p asses through, all transparent bodies with 

mission oj heat x m ... 

through bod- but slight diminution. But heat from less 
intense sources is absorbed, and in large 
part stopped by many substances which allow light to 
pass ; such are water, and alum, and glass to a less ex- 
tent. A glass plate held between one's face and the sun 
will not protect it, but held before the fire will intercept 
a large part of the heat. So a glass lens or burning- 
glass will stop the heat of a fire, instead of transmitting 
and concentrating its ra} r s, as it does those of the sun. 
It is a singular fact, on the other hand, that many sub- 
stances which stop the light, transmit heat very per- 
fectly. Such are black glass and smoked quartz crystal. 
Rock salt allows heat to pass so completely that it has 
been called the glass of heat. 

, 7 82. Reflection of heat. — Polished 

What bodies 

are the best re- metallic surfaces are the best reflectors. 

%^Z°£ ea the C ° ffee takeS l011 § er t0 b0il in a bri § ht Cof " 

subject. fee-pot, because the heat is reflected from 

the bright surface and does not enter the liquid. If it 
were desired to heat a liquid as rapidly as possible, and 
keep it hot as long as possible in the same vessel, it 
would be wise to take a dingy one for the rapid heat- 
ing of the liquid, and then to polish it in order to fasten 
the heat in. Glass mirrors do not reflect heat so well 
as those of uncovered metal, because of the absorbing 



42 HEAT. 

power of the glass, mentioned in the last paragraph. 
But this absorbing power is very slight for heat which 
comes from an intense source like the sun, so that such 
mirrors reflect the solar heat quite perfectly. 
, Tr . J . ,. 82. Absorption of heat. — Surfaces are 

What bodies 

absorb heat good absorbers, in proportion as they are 
poor reflectors. All the heat that falls on 
any surface, must be either reflected or absorbed. In 
proportion, therefore, as little is reflected much is ab- 
sorbed. 

83. Absorption continued. — Dark cloth- 

~What effect 

has color on ing is warmer than that of light color, for 
ctto^ ^ the reason > that heat associated with light 
seems to follow the laws of the latter and 
undergo absorption or reflection with it. Now we know 
that dark objects owe their dark color to the fact that they 
absorb much light, and reflect but little to the eye. Ex- 
periment shows that they absorb much heat also, if the 
heat be associated with light. The absorbed light must 
show the way, as it were, for the entrance of the heat. 
Dr. Franklin proved what has been stated, by the ob- 
servation that when different colored cloths are spread 
upon snow, it melts most rapidly under those which are 
darkest. 

84. Equilibrium of temperature. — • 

How is equili- 

brium of tem- It has before been stated that heat is con- 
peraturemain- stantly ra diated from all bodies. Absorp- 

tained ? J s 

tion of heat, is also universal. If any num- 
ber of bodies are equally hot, they remain so, each ac- 
cording to its surface, imparting to the rest and receiv- 
ing from all the others, taken together, the same quantity 



RADIATION. 43 

of heat. If one is hotter than the rest, it gives faster 
than it receives, until the equilibrium is reached. And 
if, while they are thus coming to the same temperature, 
one is a good reflector, and therefore slow to receive 
the heat which comes to it, it is also slow to part with 
what it gets ; thus the difference of reflecting power 
is without influence. 

85. Cooling of the earth. — Were it 
^ *J , lo not for the sun, the heat of the earth would 

said of the ' 

cooling of the waste away very rapidly into space. It is, 

earth? .,,,.,. . 

m fact, radiated into space now, as truly 
as if there were no sun or stars, but these make up for 
the loss. At night, when the sun is below the horizon, 
the waste by radiation takes place very rapidly, and 
the earth and air grow colder in consequence. It 
is not simply because of the absence of the direct 
heat of the sun, for this is removed at once when the 
sun sets, while the cooling proceeds until morning. 
As the earth, being solid, is a better radiator than 
the air, it cools most rapidly, sending out its heat 
through the air into space. In this way the earth often 
becomes cooled from ten to twenty degrees lower than 
the air above it. 

86. Ice in the tropics. — Advantage 

Eowisice pro- . 

duced in the is taken of the cooling which occurs by ra- 
tropics. diation, to produce ice, in countries where 

the temperature of the air does not fall to the freezing 
point. Water contained in shallow vessels, placed in 
trenches dug in the ground, to protect it from currents 
of warm air, becomes covered with ice by a night's ex- 



44 HEAT. 

posure. That the water is not frozen by evaporation, is 
evident from the fact that it does not freeze in windy 
nights, when evaporation is greatest. 

87. The formation of dew. — Dew 

Explain the 

formation of does not "fall." Its deposition is an* 
other consequence of the cooling of the 
earth by radiation. The air, however transparent, al- 
ways contains moisture, absorbed and invisible. Cold, 
causes the air, like every thing else, to contract, and 
presses out of it, as it were, the water which it con- , 
tains. Now, when at night the earth has become 
cooled by radiation, the warmer air which comes in 
contact with it is cooled, and thus made to deposit its 
moisture in the form of dew. When the temperature 
is sufficiently low, the dew takes the form of frost. 

88. Why clouds prevent dew. — Clouds 
prevent ^the send back the heat radiated from the earth, 
formation of ^y a new radiation, and thus prevent the 
cooling which is essential to the produc- 
tion of dew. No dew is found therefore, on cloudy 
nights, when, if it came from above, like rain and 
snow, we should expect most. 

89. Artificial prevention of dew 

Hoio can the T , . i -. 

formation of AND FROST. — Jt is only necessary to sun- 
dew be prevent- gtitute for clouds the artificial canopy of a 

ed artificially? rJ 

muslin handkerchief, or any other cover- 
ing, at a little distance from the earth, to prevent the 
deposition of dew and frost. Gardeners practised this 
method of protecting their tender plants from frost, 
long before philosophers explained it. 



radiation. 45 

90. Absence of dew on polished sur- 

not' deposited FACES. — Dew does not form on polished 
on polished sur f aces because they are poor radiators, or, 

surfaces. j r ? ; 

in other words, do not allow their heat to 
escape, and thereby produce the degree of cold which 
is required to form dew. Leaves and grass receive 
most dew, because they are the best radiators. 

91. Supposed radiation of cold. — 
thermometer If a piece of ice be held before a ther- 
fall when m ometer, it will cause the mercury to sink. 

Drought near J 

ice ? It is not because cold has been radiated 

from the ice, but because the thermometer, in common 
with all other bodies, is constantly giving out heat, 
and when the ice is near, it does not get its due portion 
in return. The ice cuts off the heat that would have 
come to it from other objects behind it, and gives it but 
little in its place. 

92. Refraction of heat. — Rays of 

How are rays . -• * -. • 

of heat re- heat from the sun and other objects, are 
fracted? refracted or bent out of their course, on 

passing from one medium to rc*«Sv-.. 
another, similarly to rays of SSI'S" P^Sfc. 

GREEN I^T^^S^^ ^> 

light. By ordinary glass ;Sge.^^^^^^^^^^ 

prisms most of the heat rays ^™^. ' ^ ^^ 

are refracted in a less degree. 

93. Heat rays and chemical rays. — 

7Sttr% S he l at The n g ht which proceeds from the sun, is 
rays and che- accompanied by rays of heat and others 
called chemical or actinic rays. In the 
analysis of light by a prism, the chemical rays accu- 
mulate principally in the region of'the violet color of 



46 HEAT* 

the spectrum, while the most of the heat rays are 
thrown into the region of the red, and below it. Nei- 
ther the place of the heat rays nor of the chemical rays 
is visible to the eye, but a delicate thermometer proves 
that there is most heat just below the red, and a piece 
of paper covered with chloride of silver, (a substance 
very sensitive to the chemical rays of light,) grows 
black most rapidly in the region of the violet. The 
place of the chemical and heat rays is thus shown, al- 
though neither can be seen. It is not to be understood 
that they are confined to the points indicated, but only 
that they are accumulated there in largest proportion. 

94. Burning glasses. — The collection 

acHon n % of ra Y s of heat from the sun h Y ordinary 
burning glass- burning glasses, depends on the fact that 
they are refracted, or bent out of their 
course on passing from one medium to another, pre- 
cisely as in the case of light. A lens made of two 
watch-glasses, filled with water, answers for heat as 
well as light, and may be used as a burning glass. 

95. Different heat rays. — There are 
rays of heat different kinds of heat rays, as there are of 
alike ? light rays ; some will pass through one 
substance best, and some through another. Thus, a 
piece of smoked rock salt allows the blue heat ray of 
the spectrum to pass, while alum lets the lower or 
red heat ray pass. 

96. Analysis of heat. — The analysis 

How is the ■ . .. . 

analysis of of heat is effected by the same means as 
heat effected* that of light< Rayg f the gun are passed 

through a prism just as if light were to be analyzed. 



RADIATION. 47 

a. dark co 1 / red glass being previously placed before the 
prism, to absorb the light and allow the heat only to 
pass. Emerging from the prism, it forms an invisible 
spectrum of rays beyond. These rays correspond to 
the diiferent colored rays of light, and have different 
capacities of passing through different substances, as 
before stated. But, strictly speaking, they have no 
•uolor ; they were called blue and red, simply to de- 
signate their relative position. Heat from very intense 
sources is mostly violet, and violet heat passes more 
seadily than the other rays through most substances. 
This accounts for the fact that the heat of the sun is 
not stopped by glass. For the analysis of heat from 
other sources other material must be employed. 

97. Effect of different heat rays 

What is , 

said of the IN melttng snow. — biiow melts compara- 
melting of tively slowly in the heat of the sun, for 

snow? i 

the reason mentioned in the last paragraph. 
Being from a highly heated source, it passes through 
the snow instead of stopping to melt it. But near a 
fallen tree melting proceeds more rapidly, because the 
heat absorbed as violet, is radiated again from the mod- 
erately heated source as red heat, which, falling on the 
snow in its vicinity, is readily absorbed, instead of be- 
ing transmitted. 

98. Burning glass of ice. — A lens 

How can gun- 
powder be ig- sufficiently powerful to ignite gunpowder 

nitedbyice? mfty be m ^ Q Qf j^ ln using any ^ 

it is first to be placed near the object to be ignited, 
and then withdrawn till the spot of light which it 
casts is round and very small. The focus to which 



,48 HEAT. 

all the rays of light converge is thus found. The heat 
focus is a little beyond, but so near that the difference 
need not be taken into account. 



Section 3. — Changes effected by Heat. 

99. Expansion, melting, and vaporiza- 

What changes . . 

r/re e^c^d fy tion are the principal changes effected by 
heat, while contraction, freezing, and con- 
densation of vapor are produced by its withdrawal. 
But before these changes are explained, it will be weF 
to consider certain remarkable differences in the heat 
ing effects of heat, in the case of different substances. 

100. The heating effect of heat n 

Are the effects DIFFERENT FOR DIFFERENT SUBSTANCES. 

of heat equal 

in different It might naturally be supposed that the 

bodies? . 

same quantity ot heat actually imparted 
to different substances would make them equally hot 
but this is not the case. If two heated cannon balls, of 
the same size and temperature, are cooled, the one in. 
mercury and the other in an equal weight of water, the 
mercury will be made much hotter than the water, by 
reception of the same heat. It does not simply feel 
hotter, as it might do if it were not really so, from the 
superior conducting power of the mercury, but it is 
actually so, as may be ascertained by testing the tem- 
perature by the thermometer. 

What is sped- 101- Specific heat. — If the above ex- 
ficheat* periment were varied, by cooling in mer- 

cury a bullet of one-thirtieth the bulk of that used 



SPECIFIC HEAT. 49 

for the water, the two would be brought to the same 
temperature. Mercury requiies but one-thirtieth as 
much heating as an equal weight of water, to make it 
equally hot. It fills up, as it were, with heat, more 
rapidly. The comparative quantity required by any 
substance to produce an equal elevation of temperature, 
is called its specific heat. 

102. Taking water as the standard, and 
specific heat of calling its specific heat one, that of mer- 
mercury? Of cur y i s about one-thirtieth. That of iron 

iron ? 

is about one-tenth. The specific heat of 
other substances is given in decimals in a table con- 
tained in the appendix. 

What is cava- 103. Eelative heat. — If we compare 
city for heat ? equal bulks of water and of mercury, instead 
of equal weights, we make out the capacity of mer- 
cury for heat, to be one-half instead of one-thirtieth 
that of water. The comparative capacity when thus 
estimated for equal measures, is called relative heat. 
Thus we say that the relative heat of mercury is one- 
half that of water; This method of comparison is 
seldom employed. 

Whatrelation 104 RELATION OF HEAT AND DENSITY.— 

exists between The specific heat of any substance is di 

density and m . 

capacity for minished as its density is increased. Less 
is required to indicate the same tempera- 
ture. The surplus raises the temperature. This is one 
source of the heat which is produced in hammering 
metals. In the case of gases, the diminution is nearly 
proportioned to the increase of density. In the case 
of liquids and solids it has been less carefully investi- 

3 



60 HEAT. 

gated.. In the comparison of different substances, no 
inference as to specific heat can be made from the de- 
gree of density. A substance more dense than another 
may at the same time have a greater specific heat. 
rj , .j 105. The ocean a reservoir of heat 

How does the 

ocean serve as In hot weather the ocean absorbs the heat 

a reservoir P . ., x ^ . » 

and regulator °* the sun and air. It it were an ocean of 
of heat? mercury, it would soon grow as hot as the 

air, and therefore cease absorbing ; but its capacity 
for heat is so much greater that this does not occur. 
Again, in cold weather it is constantly giving out the 
large quantity it has absorbed, but at the same time 
itself grows cool, though very slowly. It is thus a 
reservoir of heat and a regulator of climate. 

106. Fire by compression. — The fire 
^fle th of syringe, represented in the figure, is an Q 
the Fire Sy- instrument designed to produce fire 
nnge. ^ ^ e compression of air. On forcing 

the piston suddenly down, the tinder below it is 
ignited. This takes place on the principle already 
explained. The specific heat of compressed air 
is less than that of air uncompressed. When the com- 
pression takes place, the surplus elevates the tempera- 
ture and inflames the tinder. 



EXPANSION. 

107. Expansion universal. — All bodies, 

has^heaf'ol solid > li( l uid > and g aseous > expand by heat, 

the size of bo- and contract to their original dimensions on 

cooling. An iron wire lengthens by heat ; 

the mercury in a thermometer expands and rises by 



EXPANSION. 51 

heating; air partially filling a bladder expands and fills 
it by the operation of the same cause. 

How does heat ^OW HEAT EXPANDS BODIES. — All parti- 

opcrate to ex- cles may be regarded as surrounded by 
pand bodies? spheres of heat 0n i mpart i ng additional 

heat to any substance, the sphere of each atom is en- 
larged, and general expansion is the consequence. 
According to another mode of viewing the subject; 
heat produces repulsion between particles in some un- 
known way, and this occasions expansion. 

109. Expansion of solids. — The ex- 

Among solids, - . . . 

which expand pansion of solids by heat is comparatively 
t emost. small. Among solids, the metals expand 

the most ; but an iron wire increases only ¥ ^ in 
length on being heated from zero up to 212°. Ex- 
pansion in general bulk is about three times as great 
as in length. Thus, a cannon ball heated to 212° 
would occupy about 2T0 more space than when cooled 
down to zero. 

110. Illustration. — The expansion of 
f^anZl % ™tals may 

metals be it- be illustra- 
lustrated ? 

ted by ar- 
ranging a brick, a knit- 
ting-needle, and a shin- 
gle, as in the figure. On 
heating the needle with a spirit lamp, the shingle, if 
before carefully poised, will be overturned. 
What appli- m - Wheel-tires, rivets, etc.— 

cation of this Important application of even this small 

expansion is x 

made in the degree of expansion is made in the arts. 
The tires of carriage wheels, for example, 




52 HEAT. 

are made originally too small fcr the frames they are 
to surround.. They are then heated red hot and ap- 
plied in a state of expansion. The contraction which 
afterward takes place, on sudden cooling by cold wa- 
ter, binds the wooden frame-work together with the 
greatest firmness. So in making steam-boilers, the 
rivets are fastened while hot, that they may by subse- 
quent contraction unite the plates more firmly. 

112. Hot-water pipes. — In certain 

What disad- . . . 

vantages arise uses to which iron is applied, the conse- 
f rom . the ex ' quences of expansion have to be carefully 

pansion of t. r J 

metals? guarded against. A cast-iron pipe for the 

conveyance of steam or hot water, must not be so laid 
that its ends touch two opposite walls, lest by its ex- 
pansion when heated, the walls should be overturned. 

113. Clamps in walls. — If the two 

Z k s a Lldfpo1i ends of a P iece of metal are fixed S0 that 

clamps in they cannot move, and contraction takes 
place by cold, the metal must break. Cast- 
iron clamps in walls are frequently thus broken. If 
they are of wrought iron, they often crush the stone, 
and thus loosen themselves in their sockets. 

114. Lifting walls. — Walls of build- 

How are walls . . 

straightened mgs in danger of falling, have been restored 
lUTontrZ to their perpendicular position by taking 
tion - indirect advantage of expansion. This 

is effected, by connecting the walls to be lifted into 
place, by an iron rod, fixed firmly into one wall, and 
passing loosely through a hole in the other. The 
whole length of the rod is then heated by lamps, 
whereby expansion is occasioned, and the rod made to 



EXPANSION. 53 

project beyond the building. The nut with which it 
is provided is then screwed up on the projecting rod, 
until it touches the outside of the wall. The lamps 
being then removed, the rod cools, and, by its con- 
traction, draws up the walls with it. 

115. Fracture of glass vessels. — 
fracture of Glass expands less than iron by heat, yet 
glass vessels sufficiently, when expansion is unequal on 

by heat ? . . . 

opposite surfaces, to occasion its fracture. 
Thus if hot water be poured on a thick glass plate, it 
cracks. The first effect is to expand the upper surface, 
while the under one is but slightly affected. The ob- 
vious tendency of this unequal expansion, is to warp 
the plate, and curve it inward toward the under side. 
But, as the glass cannot bend, it breaks. 

116. HOW TO CUT GLASS BY HOT WIRE. 

How can heat 

be used to cut In consequence of the same unequal expan- 
giass ? sion, a crack once commenced in glass may 

be made to follow the heated end of a rod of iron or pipe- 
stem drawn over its surface. Broken vessels of glass 
may be thus cut into useful shapes. A glass vial may 
be cut evenly in two, by encircling it with a ring of 
iron heated to redness, and afterward plunging it into 
cold water. The glass beneath the ring becomes ex- 
panded through and through, and the subsequent im- 
mersion in water, causes a sudden contraction in the 
exterior, and consequent fracture, on the principle above 
stated. 

117. Wood and marble expand lit- 
Zf ar LTrbt tle.— Wood and marble expand but little 
used for pen- "by heat, and are therefore sometimes used 

dulum rods / 

for pendulum rods, where careful provision 



54 



HEAT. 



What is the 
relative expan- 
sion of water 
and iron ? 



must be made against change of length by change of 

weather. 

118. Liquids expand more than sol- 
ids. — A column of water inclosed in a glass 
tube, will expand 2V * n length on being 
heated from freezing to the boiling point 

of water, while a column of iron will expand only gy^. 

119. Illustration. — The overflow of 
expansion of water from full vessels before boiling 
liquidsbyheat commences? so often observed in the 

kitchen, is in consequence of expansion by heat. To 

illustrate the expansion of liquids, a 

test-tube full of water may be heated 

over a spirit lamp, as indicated in the 

figure. The water will be found to 

heap itself into a convex surface over 

the mouth of the tube, and even to run 

over, long before boiling commences. 

120. Cold water ex- 

What effect 

pands by cold. — There is 

an important exception to the general law 
of expansion of liquids by heat and contraction by cold, 
or withdrawal of heat. Very cold water (39°F.) expands 
by further cold before it freezes. Again, on conver- 
sion into ice, it undergoes still further expansion. 

121. Illustration. — Expansion by these 
How may ex- . 

pansionbycold combined causes may be shown by bury- 
be illustrated? j n g a tes t-tube full of water ill a mixture of 
snow and salt. Before the water is completely frozen, 
it will rise at least a quarter of an inch, and fill the 
tube.. 



has cold on 
water at Sd°F. 





EXPANSION. 55 

The greater part of this expansion is owing to 
the latter of the causes above mentioned. The 
freezing mixture employed is made of two 
parts snow to one part salt, brought into 
the cup alternately, in small portions. It 
is well to wrap the cup in flannel, or other 
cloth, to prevent loss of heat. From ten to fifteen 
minutes are required for the experiment. If the water 
is perfectly frozen, the tube will be cracked by its ex- 
pansion. 

122. Cold water floats on warmer 

collwIterfloZ WATER AND PROTECTS IT.— It Was shown 

on warmer wa- in the last paragraph that very cold water 

ter? 

(below 39°) is in an expanded condition, 
and occupies more space than warmer water. It fol- 
lows that it is lighter, and will float on warmer water. 
As the weather grows colder each winter, and the time 
approaches for the formation of ice in rivers and lakes, 
the cold water does actually float on the warmer, 
and protect it from the cold air. The body ot 
water being thus protected, ice never forms many 
feet thick. The case would be very different if water 
grew constantly heavier by cold. The surface water 
would then constantly sink, until all were reduced to 
the freezing point. Cooling does, in fact, proceed in 
this way until the temperature sinks to 39° ; then the 
exception comes in play, and the surface water, as 
before stated, retains its place and exerts its protecting 
influence. When ice is subsequently formed it has the 
same effect. 



56 HEAT. 

123. Consequences of the lightness 
What conse- 

quences result OF VERY COLD WATER. Bllt for the re- 

from the ex- mar k a bi e f ac t that more cold makes very 

pansion ofwa- J 

terbycol'di cold water lighter, and not heavier, and 
thus enables it to exert the protecting influence just 
explained, the cold of a single winter would be suffi- 
cient to kill all the fishes inhabiting our lakes and 
rivers. Another consequence would be change of cli- 
mate, as a necessary result of the formation of im- 
mense masses of ice, which the heat of the summer 
would be insufficient to melt. The temperate regions 
of the earth would thus become uninhabitable. Such 
are the consequences which are obviated by this 
remarkable exception to a general law of expansion. 
The whole realm of nature furnishes no more remark- 
able evidence of design on the part of the Creator. 

124. Some liquids expand more than 

In what pro~ 

portion do spi~ others. — Some liquids expand more by 

Sand water heat than ° therS « S P irits ° f wine > 0n be ~ 

expand? j ng heated from 32° to 212°, increases one- 

ninth in bulk ; oil expands about one-twelfth, and wa- 
ter, as has before been stated, one-twenty-third. It is 
much to the advantage of the dealer in spirits to buy 
in winter and sell in summer. Twenty gallons 
bought in January, will have become, by expansion, 
twenty-one in July. The difference between the cold- 
est and warmest weather of the year, is sufficient to 
make about this difference in bulk. 

125. Gases expand more than either 

How do gases 

compare with solids or liquids. — Gases expand more 
quids Tn ex- th an either solids or liquids by heat. The 
pansibility? reason is, that in gases there is no co- 



EXPANSION. 57 

hesion to overcome as in the two other states of 
matter. While iron increases in general bulk aroth, 
and water about £$d, on being heated from the freez- 
ing to the boiling point of the latter, air expands more 
than ^d by the same increase of temperature. 

126. Law of expansion for gases. — 

State the law _ ' ■ • » • i_- i 

of expansion Gases expand 4^oth oi the bulk which they 
for gases. possess at 32°, for every degree above that 
point, and contract in the same proportion for every de- 
gree below it. Thus, 490 cubic inches at 32° would 
so expand as to occupy an inch more space at 33°, 
still another inch at 34°, and at the same rate for 
higher temperatures. And the same quantity would 
contract by cold, or withdrawal of heat, so as to oc- 
cupy an inch less space at 31°, and two inches less at 
30°, and so on for lower temperatures. The law is 
the same for steam and other vapors. 
What is * 127. The thermometer. — The ther- 
thermometer? mometer is an instrument in which ex- 
pansion is made use of to show changes of tem- 
perature. A straight wire, which would grow regu- 
larly and perceptibly longer in proportion to the 
increase of temperature, would form the most conve- 
nient thermometer. But solids do not expand enough, 
or with sufficient regularity, for this purpose. The 
liquid metal mercury, is therefore employed instead, 
being inclosed in a glass tube and bulb. 

128. Construction; of thermome- 

How are ther- 

Mometersman- ters. — In making thermometers, the 
ufactured? mercury being first introduced into the 

bulb, is boiled, so as to expel all air and moisture, 

3* 



58 HEAT. 

and fill the tube with its own vapor. The end of the 
tube is then closed by fusion. As the metal cools, it 
contracts and collects in the bulb and lower part of 
the tube, leaving a vacuum above. The instrument 
is now complete, with the exception of graduation. 
Used in this condition, the mercury would be ob- 
served to rise and fall with changes of temperature, 
but we should not be able to say how much or how 
little. 

129. Graduation of thermometers. — 
How are -,»',. ~ . i • i 

thermometers To obtain a fixed point trom which to 
graduated? count, the instrument is immersed in melt- 
ing ice, and the point to which the mercury sinks 
scratched on the glass. This point is called zero. 
Another fixed point is obtained by immersing the 
thermometer in boiling water, and when the 
mercury has risen, noting this height also on 
the glass, and marking it 100°. The space^be- 
tween the two points is next divided into one 
hundred equal parts, by scratches on the glass, 
and numbered from one up to a hundred. The 
upper and lower portions of the tube are marked 
off into divisions of the same length, for very 
high and low temperatures. 
^ f , 130. Centigrade thermometer. 

Describe the 

Centigrade A thermometer graduated as above 
thermometer. ig called a ceintigrade thermometer, 



from the fact that the space between "boiling" and ^ 
" freezing" is divided into one hundred degrees. This 
is by far the most rational method of graduating, 
and these thermometers are in general use on the 



THE THERMOMETER. 



59 



continent of Europe, and by scientific men all over 
the world. 

131. Fahrenheit thermometer. — This 

Jjp^crihe the 

Fahrenheit is the thermometer in common use in this 
thermometer. country- The i nstr ument itself is pre- 
cisely the same as the centigrade. The difference is 
only in the graduation. In graduating it, the space 
between the freezing and boiling points having been 
marked on the glass, is divided into one hundred and 
eighty parts, and the rest of the tube, above and below, 
into similar spaces. The zero, or starting point, is 
fixed lower down than in the centigrade, 
where nothing especial happens, instead of 
where water freezes. The consequence is, 
that in counting up and affixing the numbers? 
the freezing point comes at 32°, and the 
boiling point at 212°. There is no good rea- 
son for placing the zero there, or for choosing 
such a number as 180 for the number of de- 
grees between freezing and boiling. The 
centigrade graduation is, therefore, much to 
be preferred. If a thermometer of each 
kind were immersed in boiling water, the 
mercury would rise in the centigrade to the 
point marked 100, and in the Fahrenheit ^f *§y 
to the point marked 212. In the same way, zero cen- 
tigrade corresponds to 32° Fahrenheit. The two ther- 
mometers are compared in the figure. 

How is extreme 132. EXTREME COLD, HOW MEASURED. 

coldmeasured? As the temperature is lowered, the mer- 
cury of the Fahrenheit thermometer sinks, until by 



60 



HEAT. 



sufficient cold it reaches 39 degrees below zero. 
More intense cold has no further effect, for at this point 
the mercury freezes. How much colder it is than 
— 39° cannot be told, therefore, by the mercurial 
thermometer. Thermometers containing alcohol in- 
stead of mercury are used for this purpose, because ah 
cohol never freezes, and will continue to sink furthei 
and further in the tube the colder it grows. 
xr . 133. Extreme heat, how measured. 

How is extreme 

heat meas~ If a Fahrenheit thermometer is heated, 
the mercury in it rises till it reaches 662°, 
and then begins to boil. A little more heat forms suf- 
ficient vapor of mercury to burst the tube. For this 
reason, a mercurial thermometer cannot be used to 
measure extreme heat. A platinum bar inclosed in a 
black lead tube shut at the bottom, is common- 
ly employed for this purpose. Tube and bar are 
placed on the fire, or in the melted metal, whose 
heat it is desired to measure, one end being left 
out, so that it can be seen. The consequence is 
that the platinum bar expands, and projects 
from the earthen tube. The tube itself expands but 
little. The farther the bar projects, the greater is the 
heat. As it pushes out, it is made to move an index 
hand, and point to the number indicating the tempera- 
ture, on a graduated arc. This arc is first graduated by 
repeated trials, observing how much the bar projects 
and moves the hand by the same heat which raises 
the mercury one degree in the Fahrenheit thermometer. 
134. The air thermometer. — A col- 

Describe the . ; 

air thermome- umn of air confined in a glass tube over 
Ur ' colored water, was the first thermometer 




LIQUEFACTIOxV. 61 

used. Heat expands the air and lengthens the column 
downward, pushing the water before it, while cold has 
the contrary effect. The temperature is thus indicated 
by the height at which the water stands. 

135. Illustration. — The principle of 
Illustrate the ^q a ir thermometer may be illustrated as 

principle of J 

the air ther- represented in the figure. A 
test-tube is half filled, and 
then inverted in a glass of water without | 
allowing the water which it contains to 
flow out. Heat applied to the tube will lengthen the 
column of air by expansion. 



LIQUEFACTION. 
136. Solids become liquids by heat. 

How do solids , 

become li- On being heated up to a certain point, solids 
qmds? are me i te( j j or converted into liquids. 

Thus, at all temperatures below 32°, water is solid 
ice, but the moment it is warmed up to this point, 
by change of weather or other means, it begins to 
melt. The temperature at which this change occurs 
is called the melting point. 32° is therefore the melt- 
ing point of ice. The melting point of sulphur is 
226°; that of lead, 612°. 

137. All substances are fusible. — 

Are all sub- . 

stances fusi- All substances are fusible, or, in other 
words, may be melted ; but the melting 
point of all is not definitely known. Thus carbon has 
been fused by the heat of the galvanic battery, but it 
is impossible to state the melting point in degrees. 



62 HEAT. 

Under great pressure, increased heat is required to ef- 
fect fusion. Thus the melting point of sulphur is 
raised from 226° to 285°, by a pressure of 11,880 lbs. 
to the square inch. There are exceptions to this law. 

Whatremark- 138 ' DISAPPEARANCE OF HEAT IN MELT- 

able circum- i NG . — Melting or fusing is effected by heat, 

stance attends ■■ i • 

the melting of and a remarkable circumstance attending 
bodies ? j^ j g t j le di sa pp earallce f the heat which 

has effected the change. Thus, if a thermometer be 
applied to ice or snow which has just begun to melt, 
it will be found to stand at 32°. Let the ice be then 
introduced into a tumbler, and placed on a stove, and 
the temperature again tested at the moment when the 
conversion into water is completed. The thermometer 
will be found again to stand at 32°. The water produced 
is no hotter than the original ice, yet heat has been pour- 
ing into it, through the bottom of the ves- 
sel,during the whole process of melting. 
If a piece of glass of the same size had 
been subjected to the same heat, it would 
have grown constantly hotter. It fol- 
lows that in the case of the ice there 
has been a disappearance of heat. This 
disappearance always occurs whenever 
a solid is converted into a liquid. 

What other ^^' ANALOGOUS DISAPPEARANCE OF 

instances of acidity. — Chemistry furnishes other in- 

disa T) T)ea ranee 

does chemistry stances of disappearance, which may help 
afford? us j n understanding this one. If vinegar 

be poured upon chalk it loses its sourness. It is be- 
cause a combination has taken place between the acid 




FREEZING POINT. 63 

vinegar and the lime which the chalk contains, and a 
new substance, called a salt, has been formed out of 
both. So in the present case, we may suppose that 
heat and the solid have combined to form a liquid, and 
the property of heat to effect the senses and the ther- 
mometer, has at the same time disappeared. Any liquid 
may therefore be regarded as a compound of solid and 
heat. The heat which thus disappears is called com- 
bined, or latent heat. 

Mention some l^O. FREEZING MIXTURES. When Solids 

freezing mix- take a liquid form by other means, as. for 

tures. Mow do : 

they produce example, when salt dissolves in water, the 
temperature is generally much reduced. 
Nitre, for example, reduces the temperature of water in 
which it is dissolved from 15 to 18 degrees, and is there- 
fore much used in the East, where it is abundant, for 
cooling wines. Mixed nitre and sal-ammoniac have a 
still greater effect. Sulphate of soda drenched with 
strong muriatic acid, will reduce the temperature from 
50° to zero. 
_ . , 141. When two solids, on being mixed, 

Juetitzon other 

freezing mix- become both liquid, still greater cold is 

dolhey Zrl often P roduced - T h is is the case wi *h a 

duce greater mixture of snow with common salt, or with 
chloride of calcium. By the former mix- 
ture, used as shown in paragraph 121, ice cream is frozen.* 
By the latter mixture, a cold sufficient to freeze mercury 
may readily be produced. For this purpose, three parta 
of the salt are to be mixed with two of dry snow. 

* Fahrenheit regarded the temperature thus produced as absolute cold, 
and therefore assumed it as the zero of his scate. 



64 HEAT. 

/ 

142. The melting of snow cools the 
How docs the AIR — Whenever ice is converted into wa- 

mclting oj 

mow affect the ter, whether rapidly by fire or slowly 
by change of weather, the disappearance 
of heat, above mentioned, occurs. Thus, when the 
snow melts in spring, heat is drawn off from the air 
and made latent, or combined in the water which re- 
sults from the melting. This makes the weather 
cooler than it would otherwise be, and retards in a 
measure the advance of spring. 

How do liquids 143. Freezing. — Liquids become solids 
become solids ? ^y ^ rem0V al of their combined heat. 
Thus, if molten lead be allowed to stand awhile, the 
heat which it contains passes away into other objects, 
warming them ; and the metal itself, having lost its 
heat, becomes solid. So in winter, the combined heat 
which is contained in water, is conveyed away by the 
colder air, and the water, having lost its heat, is con- 
verted into ice. 

144. Freezing point. — The tempera- 

Wkat is the 

freezing point ture at which a substance passes from the 

of a liquid f Hquid intQ the golid gtate is caUed the 

freezing point. Thus, 32° is the freezing point of wa- 
ter. The freezing point of any substance is, as might 
be supposed, the same as the melting point. Water, for 
example, becomes ice in process of cooling, at the 
same temperature that ice becomes water in process of 
heating. 

145. All liquids have their freez- 

Can all liquids 

be frozen? iNG point. — There is good reason to be- 

Give examples. iieye ^ ^ liquidSj without exception, 



I \TENT HEAT. 65 

have their freezing point, but the reduction of tem- 
perature requisite has not in the case of all been at- 
tained. Alcohol and ether, for example, have never 
been frozen. 

146. In freezing, latent heat be- 

Ja/Z27es C0MES SENSIBLE HEAT— If Water, in SUffi- 

of the latent cient quantity, is taken into an apartment 

heat? -ill 

whose temperature is several degrees be- 
low the freezing point, and then allowed to become 
ice, it will be found that the freezing process has ac- 
tually warmed the apartment several degrees. The 
latent heat has been drawn off by the colder air of 
the room, raising its own temperature, and leaving the 
water in the condition of ice. 

147. Cellars warmed by ice. — In ac- 

How can eel- . ..._.' 

larsbeicarmed cordance with the principle above stated, 
by ice ? tu ^ s Q f water are sometimes set to freeze 

in cellars, thereby to prevent excessive cold. And 
even in the coldest climates a sufficient supply of wa- 
ter might thus be made to secure an apartment against 
extreme cold. 

148. Effect on climate. — The milder 
has^he ffeez- c li mate °f ^ e vicinity of lakes which are 
ing of water accustomed to freeze in winter, and the 

on climate ? . n n 

moderation of the weather during a snow 
storm, are accounted for on the same principle. As the 
melting of snow retards in a certain degree the ad- 
vance of spring by the heat it abstracts from the at- 
mosphere, so the formation of ice tends to make the 
advance of winter less rapid, by the heat which it 
evolves. 



66 HEAT. 



VAPORIZATION. 

WJiat is said of 149. Formation of vapors. — Unlike melt- 
the formation of j n ~ or liq Ue f ac tion, vaporization occurs 

vapors s ° ■*■ 1 r ,, 

gradually, and through a wide range o* 
temperature. Thus water at all temperatures, and 
even ice, yields vapor. But there is a limit for each 
substance below which its evaporation does not occur. 

150. Vapors transparent. — All vapors 

What is the r 

appearance of are perfectly transparent, like the atmo- 
vapors. sphere. If water is boiled in a flask, it 

will be found that the steam within the flask is as 
transparent as air. The steam thrown from a locomo- 
tive would be invisible if it remained steam. We 
should hear its roar, but see nothing. 

151. Density of vapors. — -Vapors are 

Is the density n . 

of vapors uni- of all degrees of density. The vapor of 
f or water may be as thin as air, or, again, al- 

most as dense as water itself. 

152. Elasticity of vapors. — All va- 

lllustrate the , 

elasticity of pors are elastic, like air. Steam, like air, 
vapors. y? compressed in a cylinder, with a close 

fitting piston, by a heavy weight, would expand again, 
and force the piston out, as soon as the weight were 
removed. The force with which a vapor expands, or 
strives to expand, supposing the weight not removed, 
is called its elastic force or tension. 



VAPOR. 67 

How does tern- *53. DENSITY DEPENDS ON TEMPERATURE. 

perature affect — The vapor produced at ordinary tempera- 
tures by evaporation from the sea and the 
moist earth, is less dense, or, in other words, contains less 
water in the same volume, than that formed during the 
heat of summer. Ordinary steam, or aqueous vapor, pro- 
duced at 212°, has still greater density. Steam produced 
at 250° has double the density of ordinary steam,. and by 
increasing the temperature to 29i°, the density is again 
doubled. Steam of higher temperature than 212° can 
only be produced in closed vessels, or those with an 
imperfect vent. The law is the same in the case of 
other vapors — the higher the temperature the greater 
the density, provided a surplus of the material from 
which the vapor is produced is present. But if this 
is not the case, heat has simply the effect of expand- 
ing the vapor as it would an equal quantity of air. 
In the case of a partial supply of water, the vapor 
grows more dense, but does not reach the highest 
density which it would have at the same temperature 
with a full supply. 

Whatremark- 154 DISAPPEARANCE OF HEAT IN VA- 

able circum- pors. — The same disappearance of heat 

st cuice atteixds 

the formation which occurs when a solid is converted 
of vapors ? ^ Q a j [^[^ occurs also when a liquid is 
converted into a vapor or gas. Thus, if we wish to 
cool a room in summer, we sprinkle the floor. As the 
water evaporates, much of the heat of the room dis- 
appears. It has entered into combination with water 
to produce vapor, and has no longer the power of af- 



68 HEAT. 

fecting the senses and the thermometer. In the same 
manner, our bodies are cooled in summer by the con- 
stant evaporation of moisture from the surface. All 
vapors may, indeed, be regarded as combinations of 
heat with the liquids from which they are formed. In 
this case, also, the heat which becomes latent in thus 
combining, is called latent heat. 

155. Freezing by evaporation. — The 

How can ether 

be made to more rapidly a substance evaporates, the 
fixplain" ^its niore heat does it require for the evapora- 
action. tion. This it obtains from objects in con- 

tact with it. Ether may be made to evaporate so 
rapidly as to freeze water, even in summer. This is 
best accomplished by covering the bottom of a test- 
tube with a cotton rag, or several layers of porous 
paper, as represented in the figure, dipping it into 
ether, and then waving it to and fro in the 
air, or spinning it between the palms of the hands. 
By repeating this process several times, a few ||i| 
drops of water, previously placed in the tube, may ^ 
be frozen. A mixture of liquefied carbonic acid and 
nitrous oxide gases, previously liquefied, produce on 
evaporation a temperature of 220 degrees below zero. 
156. Protection from heat by eva- 

How does evar 

poration pro- poration. — By previously moistening the 
ectfro teat. fj n g erSj they may be dipped unharmed, for 
an instant, into molten lead, or passed through a stream 
of white-hot iron as it flows from the furnace. A 
cloak of comparatively cool vapor is formed from the 
moisture upon the fingers, and keeps them from con- 
tact with the molten metal. 



VAT OH. 69 

157. Relations of air and vapor. — 

-Does vapor rpj^ g^^ j s surrounded by air to the 

displace air f J 

depth of fifty miles. It is also surrounded 
by vapor occupying the same space which the air oc- 
cupies. But they are independent of each other. 
Each contracts for itself, and expands for itself, accord- 
ing to the temperature. When more vapor is produced 
by evaporation from the sea, or other sources, it rises 
into the air without displacing it or pushing it aside, 
only rendering the vapor which it before contained 
more dense, 

158. Quantity of vapor in the at- 
tPof qU v7por mosphere.— The air is always full of va- 
exists in the p r ; that is, where there is a cubic inch 

of air, there is a cubic inch of vapor with 
it, occupying the same space. 

159. Quantity of water the air may 
^quantittof contain as vapor.— As the density of vapor 
water in the air i s dependent on temperature and the supply 

depend? . . . . . 

of material to be vaporised, it is obvious 
that the quantity of water present in the air in the form 
of vapor, varies according to temperature and locality. 
In summer, and over the sea, it is commonly greatest. 
At a medium summer temperature of 75 degrees, the 
vapor in the air is sometimes so dense that every cubic 
yard of air contains a cubic inch of water, in this form. 
But it can never, at this temperature, contain more. 
It is then said to be " saturated," and also that its capa- 
city for water is filled. 



ro 



HEAT. 



What eject JgQ. CAPACITY OF THE AIR FOR WA- 
has heat vpon at t 

the quantity of TER INCREASED BY HEAT. As the Weather 

vapor present g rows warmer, the capacity of the air 
for moisture is increased, so that at 100°? 
it can contain twice as much as at 75°, or two 
cubic inches. On the other hand, as the weather 
grows cooler, its capacity is diminished, so that at 50° 
it can hold scarcely more than half a cubic inch, and is 
saturated by this comparatively small quantity. And, 
in general, the capacity of the air for moisture is in- 
creased by the elevation of its temperature. 

161. Effect of wind. — Wind causes 
afemeqian. evaporation to proceed more rapidly, not 
tity of vapor because the air in motion has any greater 

in the air $ „ .. _ 

capacity lor moisture, but because new 
portions of air are brought successively into contact 
with the wet surface. As fast as one portion has im- 
bibed a certain amount of moisture, another portion of 
drier and more thirsty air takes its place. 

162. Deposition of moisture. — It fol- 

Explain the 

deposition of lows that air that is saturated, or, in other 
words, has its full portion of moisture ir 
the form of vapor, must deposit a portion of it in the 
form of water in cooling. Thus a cubic yard of sat- 
urated air at 75°, on being cooled down to 50°, would 
yield half a cubic inch of water, or half of the whole 
quantity which it originally contained. If we sup- 
pose the experiment to be performed in a glass vessel 
where the effect of cooling could be observed, we 
should first see a mist or dew within the box, consist- 
ing of the particles of water which the colder air can 



VAPOR. 71 

no longer retain. This mist would gradually deposit 
and collect in the form of water, and if measured, 
would be found to make more than half a cubic inch. 
Something less than half a cubic inch would remain 
as invisible vapor in the cooled air. If the air were 
cooled further, part of this would be condensed to 
water. 

What is 163. Unsaturated air. — Air that does 

said of unsat- not con t a in its complement of water will 

uratcd air and r 

its moisture ? not yield any by slight cooling. It would 
be like slightly compressing a half-filled sponge. But 
as the cooling proceeds, the vapor becomes so dense 
that further cooling will cause a deposition of moisture. 
A cubic yard of air at 75°, containing only half a cubic 
inch of water in the form of vapor, would yield none 
on being cooled do wn to 50°. At this point the formation 
would commence. If it contained originally less than 
half a cubic inch, it would have to be cooled still lower 
before any moisture made its appearance. The less 
the moisture, in short, the more cold it would require 
to wring it out. 

Is the quantity 164. QUANTITY OF VAPOR IN THE AT- 

tZyhwal- mosphere.— As has been already stated, 
wa-/s jyropor- the capacity of air for vapor is in propor- 
tion^ to its . . . rwii • j*1 

XV,-- th? tion to its warmth. The air of summer 

cai therefore contain more than that of winter ; and 
it trequently does so. But this is not necessarily the 
{-. d, for the capacity for moisture is not always filled. 
air over a desert, for example, contains less mois- 
ture than cold air over the sea. And in the same lo- 
cality, and during the same season, the quantity of 

4 



72 HEAT. 

moisture in the air will differ from day to day, and 
from hour to hour. This will depend a good deal on 
the wind, whether it blows from the land or from the 
sea. Sometimes it contains a cubic inch of water in 
the form of vapor in every square yard, but generally 
less. 

165. Mist and fog. — These are 

What is the . 

cause of mists aqueous vapor, rendered visible by the 
and fogs? cooling of the air, as before explained. 
When the air is saturated, the least cooling will pro- 
duce a fog, as in the case supposed in paragraph 162. 
When it is not saturated, more cooling will be required, 
as in the case supposed in the subsequent paragraph 
The beautiful veil of mist, which forms in summe 
nights over low places, is owing to the cooling of the 
air below its point of saturation, which takes place 
after sunset. 

166. Mixed currents of air. — The 
froSion h of Phenomena of mist, fog, clouds, and con- 
fogs by mixed sequently of rain, are more commonly 

currents of air, . . „ , , , 

owing to the mixture of cold and warm 
winds or currents of air. When this admixture takes 
place, the warm air becomes colder, and tends to de- 
posit its moisture, and the cold air warmer ; and it 
might be at first supposed that those two influences 
would counteract each other. For example, if a cubic 
yard of air at 100° mixes with a cubic yard at 50°, they 
both become 75°, and it might be thought, that the 
warming of the colder cubic yard would increase its 
capacity for moisture, as much as the cooling of the 
Warmer cubic yard would diminish its capacity, and 



FOG. 73 

that consequently no mist would be produced. But, 
as before stated, it has been ascertained by experiment 
that hot air at 100° will contain about two cubic inches, 
and air at 50°, about half a cubic inch of water. The 
two would therefore contain two and a half cubic 
inches. But air at 75° can hold but one cubic inch, 
and consequently the two cubic yards would hold but 
two cubic inches. The surplus half inch would con- 
sequently take the form of visible moisture, called 
cloud, fog, or mist, according to circumstances. It is 
not to be understood, from what is above stated, that 
half a cubic inch of water is always yielded by every 
two cubic yards of air at 50° and 100° which come to- 
gether ; if they are not totally saturated, the quantity 
will be less. 

167. Fogs on the sea coast. — The 

Why are fogs . . 

produced mi sea is cooler than the land in summer, and 
seacoasc. warmer j n winter. As a consequence, the 
air above the sea is cooler in summer and warmer in 
winter, than that above the land. The admixture of 
these bodies of air, which takes place along the coast, 
produces fogs on the principle above stated. 

168. Fogs on rivers. — When land and 

Why do fogs 

form on riv- water have the same temperature, as may 

be the case with small lakes and rivers, 

the difference of radiation during a single night often 

produces fogs. The land cools more rapidly than the 

water. As a consequence, the air above the land is 

cooler than that above the water. As the two bodies 

of air mingle, fog is produced, and is seen following 

4 



74 HEAT. 

the devious course of the river, or brooding over the 
lake in the morning. 

lf>9. Newfoundland fogs. — The fosrs 

What, causes . ° 

fA« Newfound- on the banks of Newfoundland are owing 
tndfogs. tQ t j ie m i xture f ^j^ w i n d s from the 

north, with the warm air of the gulf stream, which 
passes along that part of the ocean. 

170. Cloud-capped mountains.— -The 
clouds' 1 pro- temperature of the air at high elevations 
duced on high is always lower than at the general level 

mountains? 

of the earth. As the warm breeze comes 
up from the warmer valleys, the two currents min- 
gling, produce clouds. A clear atmosphere through- 
out a whole day is rare, on high mountains. 

171. Dew point. — It has been already 
What is the geen ^^ a « r ^ t0 ^ e c00 j e ^ m0 re or less 

dew point ? 

before it yields moisture, according to the 
amount which it contains. If it contains about one 
cubic inch to the cubic yard, or, in other words, is satu- 
rated, the least cooling will cause the appearance of 
visible moisture. If it contains half as much, it must 
be cooled down to 50° F. If it contains less than half 
as much, still more refrigeration is required. The 
temperature at which the deposition be- 
gins in any case is called the dew point. 

172. HOW TO FIND THE 

How can the 

dew point be DEW POINT. It is COmmon- 

foun . jy found by adding ice, lit- 

tle by little, to a glass of water con- 
taining a thermometer. As the water 
grows cool, the glass cools also, and as a 




DEW. 75 

consequence, the exterior air immediately in contact 
with it. After a time, moisture begins to deposit. The 
temperature at which this occurs is noted, and is the 
dew point. 

173. Dew. — The earth cools, as has 

Explain the _ . 

formation of before been stated, every clear night, by 
dew ' radiation. The air in immediate contact 

with it, becomes thereby so much cooler, that it cannot 
retain all its water in the form of invisible vapor, and 
the deposition of the surplus in the form of dew is the 
consequence. 

174. Grass and foliage receive most dew 
wdfoUaqerl because they are good radiators, and losing 
eeive the most their own heat most rapidly, cool down 

dew ? 

the air sufficiently to cause a deposition of 
its moisture. The soil itself, and stones, receive less, 
or none at all, because they do not, by their own ra- 
diation, become sufficiently cool to produce the same 
effect. Dew does not form on a cloudy night, because 
the clouds radiate heat to the earth and thus prevent 
the requisite cooling. 

175. Capacity for vapor : expansion 

How is it T , , ■, j 

known thatthe N0T THE cause.— It must not be supposed 
increased ca- that the increased capacity of air for va- 
for moisture por, which results from heating, is owing 

%pan\itn 6 ? '° to its ex P ansion * Air does indeed expand 
about one-twentieth between 50° and 100°, 
but its capacity for moisture is quadrupled by the same 
rise of temperature. 



76 HEAT. 

What proves ^^' ABSORPTION NOT THE CAUSE. — It is 

that absorption no t uncommonly supposed that the air acts 

is not the cause? . , ■* 1 

to absorb vapor as a sponge does to draw 
up water. The term "saturated" used for convenience 
in scientific works, is calculated to give this impression. 
But vapors are found to rise, even more rapidly, into a 
vacuum, or space from which all the air has been 
removed. 

Wliat then is 177. INCREASED DENSITY OF YA POR THE 

the cause? cause. — The air receives any vapor that 
may be formed, whether more or less dense. At higher 
temperatures, denser vapor is produced. It follows that 
the air will contain more water, in proportion to the 
elevation of its temperature. 

178. Removal of air does not increase 

Does the remov- -r, • i . -t 1,1, 

al of air influ- THE quantity.— It might be supposed that 
ence the forma- more water would rise into a vacuum in 
vapo ^ e f orm f vapor than into a space filled 
with air, on the ground that the removal of the air 
would make more room for something else. It is found, 
however, that the presence or absence of air makes no 
difference in the quantity.* 
_ , 179. Several vapors may occupy the 

Do vapors and 

gases exclude same space. — It follows from the last para- 
each other? g rap h that vapors do not displace the air; 
they penetrate it instead. And it is a remarkable fact, 
that a number of vapors may occupy the same space 
without interfering with one another ; and each in the 
same quantity as if the rest were absent. 

* This statement relates to vapors rising into a confined space. In 
unconfined space, expansion of the mixture occurs, which is equivalent to 
displacement in the same proportion. (§ 181.) 



VATOR. 77 

Give examples. 180. As much water will rise in vapor 
into a jar of air as if it were a vacuum. And in addi- 
tion to this, as much alcohol and ether successively, as 
if the jar were entirely empty. 

Why is moist ^1. If the elastic force or tension of air 
air lighter than is increased, it expands. Yapors possess 

dry air / , ,. „ ,. . . „ 

elastic iorce as well as air. A mixture of 
air and vapor has the combined tension of both. The 
tension of aqueous vapor at 80°, being ^L-th that of the 
air, it produces, on rising into the air, an expansion of 
s^th.* As the weight of the air is not increased in the 
same ratio, ordinary moist air is lighter than dry. 

BOILING. 

182. Weight of the atmosphere. — 
fZeTtkatthe As an introduction to the subject of boil- 
atmosphere m g ? it will be necessary to consider the 

has weiaht & 

pressure of the atmosphere. The earth is 
surrounded by an atmosphere, estimated to be fifty miles 
high. It is very light compared with the earth itself, or 
with water. But it has weight, as may be proved by 
weighing a bottle full of air, and then pumping out 
the air and weighing it again. The empty bottle will 
be found to weigh less than the bottle full of air. 

183. Another proof of the weight 

Give another . 

proof that air of the air. — I hat the air has w r eight, IS 
has weight. agam prove( j ^ tymg a p j, ece f bladder 

* Steam at 212° having tension equal to that of the air, would double 
the volume. Gases and vapors, with the density they possess when 
collected in the usual manner, by displacement of mercury or water, would 
have the same effect, and thus, like steam, displace their own volume of air. 



78 HEAT. 

over a glass cylinder, open at both ends, placing the 
open end air-tight on the plate of an air pump, and 
then exhausting the air. The pressure of the column 
of air that stands on the bladder is sufficient to break 
it, and the air settles in, as effectually as if it were a col- 
umn of iron. The atmosphere exerts such pressure, 
amounting to about fifteen pounds to every square inch, 
on all parts of the surface of the earth. 

184. A SIMPLE MEANS OF PROOF. 

DeSC7"hbe CL 

simple means Wind a stick with cotton and press ^ 
trl ng has ^ to the bottom of a test-tube, con- 
weight. taining enough water thoroughly to 

moisten it. It will be found difficult to withdraw 
the piston. The difficulty arises from the fact that 
the column of air which rests upon it, must be 
lifted at the same time. Having raised it a little way 
and released it, the piston flies with force to the bot- 
tom, owing to the weight of the same column of air. 

185. Elastic force of the atmosphere. 
Z'Z'deiZ Every cubic inch of air at the surface of 
its elastic the earth, may be likened to a piece of in- 
dia-rubber, which has been compressed into 

the space of a cubic inch, by a heavy weight placed on 
it. If we suppose a piece of rubber, while thus com- 
pressed, to be confined in a strong metallic box, it would 
evidently exert an elastic force in all directions, equal 
to the force which compressed it. So the lower por- 
tions of air, which are kept compressed by the air 
above, exert elastic force. And it is better to regard 
the pressure of fifteen pounds on every square inch of 



PRESSURE OF THE ATMOSPHERE. 



79 



Why are ice 
not crushed by 
the pressure of 
the atmo- 
sphere i 



the surface of the earth, as a consequence of the elastic 
force of the lower portions of air, rather than the direct 
effect of the weight of the whole air. The weight of 
the whole atmosphere produces the elastic force of the 
lower portions by compressing them, and the elastic 
force of the lower portions exerts the pressure. 

186. Why the pressure of the air 
does not crush us. — If a thin glass ves- 
sel were turned upside down, and air-tight, 
upon a table, it would collapse but for the 

fact that it is filled with air, which, according to the last 
paragraph, has elastic force equal to that of the air 
without. So our bodies would collapse, but for the fact 
that our lungs, and all of the cavities of the body, are 
filled with air, possessing the same elastic force as the 
external air ; a force which it had acquired by compres- 
sion, before it was taken into our bodies. 

187. Quantity of water the pres 

sure of the air will sustain. if a 

tumbler is filled under water, and then 
lifted to the surface, as 
represented in the fig- 
ure, it is well known that the wa- 
ter will not run out. The pressure 
of the atmosphere on the surface of 
the water outside, keeps the water forced up on the in- 
side. 

188. The effect would be the same if 

What quanti- . 

ty of water the tumbler were twice as tall, or if we 
«*«L/n / ^ su PP ose lt lengthened into a tube thirty- 
three feet long. If a still longer tube 



What sustains 
the water in 
the inverted 
tumbler repre- 
sented in the 
figure / 




80 HEAT. 

were used, it would be found that the level 
of the water inside, would never be more than 
thirty-three feet above the level outside. The 
remainder of the tube would be empty, as re- 
presented in the figure. In other words, the 
pressure of the atmosphere will sustain a col- 
umn of water thirty-three feet high. Water 
rises in a pump from this cause. 

189. Quantity of mercury the 

How many 

inches of Lev- PRESSURE OF THE AIR CAN SUSTAIN. 

cury will the j n performing the experiment of 
the last paragraph with mercury, it 
will be found that the level within the tube, will 
be thirty inches above the external level. In other 
words, the pressure of the atmosphere will sustain a 
column of mercury thirty inches high. 

190. If a long tube is used, there is, of 

Explain the . 

Toriceliian course, an empty space above. This is 
vacuum. called the Toricellian vacuum, from the 

fact that a vacuum was first produced in this manner by 
an Italian philosopher, named Toricelli. It is not an 
absolute vacuum, a small portion of mercury being al- 
ways present in the space in the form of transparent 
vapor. 

191. Boiling. — Thus far we have con- 

rV/iat is meant 

by the term sidered solely the formation of vapors from 
boiling? the surfaces of ii qil ids. But where any 

liquid is heated up to a certain point, vapor forms in 
bubbles below its surface. The production of vapor 
with ebullition is called boiling. 



BOILING. 



81 



How much 
steam do cubic 
inches of xca- 
ter, alcohol, 
and ether re- 
spectively pro- 
duce ? 




„ , 192. Water begins to boil when it is 

WJtat is the ° 

boiiimj point heated up to 212° ; alcohol, at 173° ; and 
v/ether? ether, at 96°. As the proper temperature is 
Of alcohol ? fi rst reached at the bottom of the vessel, 
near the fire, the formation of bubbles begins there ; 
and as the surplus heat comes in below, they continue 
to be formed at this point. 
Every liquid has its own boil- 
ing point. 

193. Expan- 
sion IN BOILING. 

A cubic inch of 

water boiled in 

an open vessel, 
produces 1696 cubic inches 
of steam. A drop one-tenth of an inch in diameter, 
would make enough to fill a sphere of the diameter 
of one and a fifth inches. A cubic inch of alcohol 
produces about 500 cubic inches of alcohol vapor ; one 
of ether about 250. The ether vapor is most dense, 
that of alcohol next, and the steam 
least so. 

194. Disappearance of 

HEAT IN BOILING. If a 

thermometer is held in 

boiling water, it indicates 
a temperature of 212° F. Continue 
the fire, and although heat constantly 
passes up into the water through the 
bottom of the vessel, it grows no hot- 
ter. The steam which is produced has 
4* 



What is said 
of the disap- 
pearance of 
heat in boiling? 




82 HEAT. 

also precisely the same temperature. Neither water 
nor steam is hotter, although both have been con- 
stantly taking in heat. But the heat has not been 
without effect, any more than in the conversion of a 
solid into a liquid. It has combined with the liquid 
to form the steam. In this case, also, the heat which 
disappears is called latent heat. 

195. Relation of pressure to boil- 
Hoxodoespres- ing. — In order that a bubble of steam may 
TJili?ig P ?° Se form, it is necessary that a small portion 
of water, shall expand into a comparatively 
large portion of steam to form it. But the atmosphere 
is constantly pressing on the surface of the water, and 
acting through the water, in all parts of the vessel, to 
prevent any separation of particles or expansion. The 
case is similar to that of a piece of india-rubber com- 
pressed beneath a mass of iron : it cannot expand ow- 
ing to the weight of the iron. 

196. Heat overcomes pressure. — But 

Explain how 

heat overcomes if we could by some means increase the 
pr€ ' elasticity of the india-rubber, it would ex- 

pand and lift the iron. So, if we can in any way iu- 
crease the tendency of the particles of water to sepa- 
rate, it will finally be strong enough to overcome the 
pressure of the atmosphere above and affect separation. 
Heat has this effect. As the water becomes hotter, 
the tendency of its particles to fly apart becomes 
greater and greater, till, at last, it is sufficient to over- 
come the pressure which has before crowded them to- 
gether, and a bubble of steam is formed. Others im- 
mediately follow, and boiling thus commences. This 



BOILING. 



83 



takes place at 212° Fahrenheit, which is therefore called 
the boiling point of water. 

197. Effect of height on boiling. 

Wliat effect ,'-■-■ i • • 

has height on At great elevations, the atmosphere is, in 
boiling i fact ^ lighter, and there is less of it above 

us, and the consequence is that water boils on moun- 
tains, at a lower temperature than in the valleys below. 
It is found, by careful observation, that an elevation of five 
hundred and fifty feet above the level of the sea, makes 
the difference of one degree in the boiling point. 

198. Measurement of altitudes. — 
heTghtTf thC This fact once established, a tea-kettle and 
mountains be a thermometer are the only requisites for 

cletevTninecl ^ 

taking the height of a mountain. The 
summit being reached, the tea-kettle is boiled, and 
the heat of the water tested by the thermometer. 
If the mercury stands at 211°, it is known that the 
height is 550 feet ; if at 210°, the height is 1100 feet ; 
and at whatever point it stands, it is only necessary to 
multiply 550 by the number of degrees depression of 
the mercury below 212°, to ascertain the elevation. On 
the top of Mont Blanc, water was observed by Saus- 
sure to boil at 184°. This gives us the means of calcu- 
lating very closely the height of that mountain. 4 
„„ „ 199. Effect of depth on boiling. — 

What effect 

has depth on In mines the atmosphere is heavier, and 
cung. there is, beside, more of it above us, than 

at the surface of the earth. Water must, in consequence, 
be more highly heated before it will boil. 550 feet 
makes, as before, a difference of one degree. We are 
thus provided with a simple means of determining the 



84 HEAT. 

depth of mines. Owing to various causes, the atmo- 
sphere at the same elevation is a little heavier some 
days than others, so that the height of a mountain or 
the depth of a mine, as thus measured, would not be 
always precisely correct. 

200. Artificial change of boiling 
bomng a7l potnt point.— It is obvious, from what has already 
of liquids be been stated, that all it is necessary to do to 

changed? „. . 

change the boiling point, is to change the 
pressure of the atmosphere, on the surface of the water 
to be boiled. To produce this change of pressure, it is 
not necessary to ascend mountains, or to descend into 
mines ; it may be done by removing the atmosphere 
by artificial means. This would be done by attaching 
a tube, air-tight, to the mouth of a test-tube or 
flask and drawing off the air by means of an 
air pump. Cold water may thus be caused to 
boil. So by pumping more air into the flask, the 
pressure would be increased, and the boiling point 
elevated ; and by this means boiling water 
would be prevented from further boiling. This 
subject is further considered in paragraph 204. 

201. Culinary paradox. — Boil some wa 

Tj p^cYioe the 

cuiinhry 'par- ter in a test-tube, and then cork it tightly, 
adox ? while steam is still issuing from its f\ 

mouth. Though removed from the fire, the wa- fe|- 
ter will continue to boil. This will be best 
observed by inverting the tube, as the bubbles of 
steam form more rapidly from the cork surface 
than from the glass. A few drops of cold water 
sprinkled on the tube will occasion a more violent 




STEAM. 85 

ebullition ; while on the other hand, boiling water, 
or the application of flame, will cause the boiling to 
cease. 

202. Explanation. — The principle is 

Explain the . . 

principle of the same as m the experiment of para- 
ge culinary h 2 ()0. As the steam condenses, by 

paradox. or > j 

the cooling influence of the air, a partial 
vacuum is produced, with diminished pressure, which 
enables the water to boil with less heat. Cold water, 
by condensing the steam and removing the pressure 
more perfectly, increases the ebullition, while boiling 
water or flame renews the steam, and consequent pres- 
sure, and therefore checks boiling. 

203. Water hammer. — The test-tube 

JjcscrtuP the 

" Water Ham- prepared as above, is a simple form of the 
mer ' u water hammer." If very thoroughly 

cooled, and then shaken with the kind of motion which 
would be required to make a bullet rise half way in 
the tube and fall again, the water will strike like lead 
on the bottom. It is because there is no air and but 
little vapor present to break its fall. 

204. Sugar boiling. — When syrup 

How may sy- . 

rup be boiled is boiled down under the ordinary pres- 
belowZU^K? gure of the atmosphere, it is apt to be 

browned or injured in flavor. By boiling it in a pan 
with an air-tight lid, and pumping off the air, and the 
vapor as fast as formed, boiling may be easily effected 
at a temperature as low as 150°. This method is put 
in practice by sugar boilers, and the disadvantages above 
mentioned are thus avoided. 



86 HEAT. 

■ ., 205. In cooking, this method could 

Can food be 

cooked by the not be employed. The water might, in- 

samc method ? dee( j be ma( j e tQ hQJl ^ 18Q0 ^ but the boiHng 

water, owing to its less heat, would not have the effect 
of water boiling at 212°. Many vegetable juices and 
infusions which are used for medicines, and would be 
injured by a high temperature, are boiled down, like 
sugar syrup, under diminished pressure. 

206. Singing of the tea-kettle. — 

Explain the . , 

singing of the The singing sound which precedes boiling, 

tea-kettle. j g owing to the C0 Hapse of the first bubbles 

of steam, as they rise into the colder water above. 

The very first bubbles that form are not steam, but air 

which the heat expels. Steam bubbles are then formed, 

which rise a little way, and, being reconverted into water, 

contract, and finally collapse. If the heat is continued 

and the water made hotter, the next are able to rise 

further. Finally, when the water becomes as hot as 

the bubbles, they make their way through, and boiling 

is thus commenced. 

What is a 207. Steam boilers. — The boiler is the 

steam boiler? vessel in which steam is formed. From 

the boiler it passes to other parts of the apparatus to 

move the machinery. Steam boilers 

are of various forms, but are always 

made of great strength, to resist the 

internal pressure to which they are 

subjected. 

Explain the 208. The figure repre- 

fgure. sents an or ainary steam boiler, with 




STEAM. 87 

the pipe which conveys the steam to the engine. A 
safety-valve is also represented, which will be more 
fully explained in another paragraph. 

209. Elastic force of steam. — Undei 

How great is . . 

the elastic ordinary circumstances, the elastic force of 
force of steam? steam is obviously equal to the elastic force 
or pressure of the atmosphere. A man who rises from 
a chair with a fifty-six pound weight on his shoulder, 
must exert an extra muscular force, equivalent to fifty- 
six pounds, in rising ; and he must continue to exert it 
while he stands. So every bubble of steam must have 
an elastic force equal to that of the air which it lifts, or 
it cannot be formed under the pressure of the atmo- 
sphere, or continue to exist when once formed. 

210. Elastic force, how increased. 

dZit% k rceof AS l0n § aS the VeSSel > in Which Steam is 

steam increas- made, is open, the pressure is as stated in 
the last paragraph. But if the boiler is 
closed steam-tight, and the heat continued, more steam 
forms, and, crowding into the same space above the 
water increases the pressure. In other words, the space 
becomes filled with denser steam, of greater elastic 
force ; and the force is finally sufficient to burst the 
boiler, unless it can find some vent. 

211. Increased temperature accom- 

What accom- n, /• 

panies in- PANIES INCREASED PRESSURE. Steam 01 

creased pres- high elastic force can only be made in a 

sure of steam ? 

close vessel. But in proportion to the 
increase of elastic force, is the increase of pressure on 
the surface of the water. Therefore, the boiling point 
becomes higher and higher, or, in other words, the wa- 



88 



HEAT. 



ter has to grow constantly hotter, in order that steam 
may form ; and as steam always has the temperature 
of the water with which it is in contact, the steam 
grows constantly hotter also. 

212. The exact relation of tempe- 

Hoxo can the 

exact relations RATURE TO PRESSURE. It is desirable to 

toire m £TpreB- know ^ e increase of pressure for each ele- 
mre be deter- vation of temperature. A steam boiler sup- 
plied with a barometer gauge and a thermo- 
meter affords the means of ascertaining this rela- 
tion. Or it may be done by a very small boiler, made for 
the purpose. The barometer gauge is nothing more than 
a bent tube fitted into the boiler, open to the air at the top, 
and containing quicksilver in the lower part of the bend. 
We will suppose all the air to have 
been expelled from the boiler, the stop- 
cock through which it made its escape 
closed, and the whole interior to be 
filled with steam. As more steam is 
produced, pressure is increased, and 
the temperature of both water and steam rise, as before 
explained. 

Whatpressure 213. Where the temperature has 
has ueam at rea ched 250°, it is found that the pres- 
et 294 ? How sure of the steam, acting on the surface of 
Is this shown? t k e quicksilver, is sufficient to force and 
hold the latter thirty inches higher in one arm of the 
tube than in the other. But the steam with which the 
boiler was filled when the stop-cock was closed, ex- 
erted a pressure of fifteen pounds per square inch, just 
sufficient to balance the pressure of the external air, and 




STEAM. 89 

prevent its forcing the quicksilver before it and crowding 
into the boiler through the tube. As before stated, when 
the thermometer reaches 250°, it is found that the denser 
steam will not only balance the atmosphere, but has 
force enough to lift the mercury thirty inches, which is 
equivalent to another atmosphere. Steam at 250°, and 
in contact with water, is therefore said to exert a pres- 
sure of two atmospheres, or thirty pounds to the square 
inch. At 275° it has a pressure of three atmospheres ; 
and at 294°, of four. )k 

What is said 214. [ALL VAPOR HAS ELASTIC FORCE. 

of the elastic rp^ apparatlls j ust described shows the 

force of vapors rr ° 

at low tem- pressure of steam at and above 212 degrees. 
pei But vapor of water has elastic force at all 

temperatures. This is best shown by passing a little 
water up into a Toricellian vacuum, and observing the 
effect. The water is introduced by blowing it 
through a glass tube, one end of which is brought 
under the mouth of the inverted tube. The 
drop rises and floats on the mercury, and as 
vapor forms at all temperatures, a portion of 
it is immediately converted into vapor. At 
the same time the level of the mercury is de- 
pressed. It is crowded down in opposition to 
the pressure of the air outside, by the elastic 
force of the vapor formed. For the sake of 
simplicity, the space above the mercury was 
supposed to be a vacuum, but the effect is the 
same as if it is filled with air. For, as has 
been already shown, vapor is produced as well in 
air as a vacuum, and with the same elastic force. If 
the top of the tube is warmed, denser vapor is formed 



90 HEAT. 

possessing greater elastic force, and the mercury sinks 
lower, till at 212° the elastic force within, is equi- 
valent to the pressure of the atmosphere without, and 
the mercury is pressed down to the external level.] 
Explain the 215. Barometer-gauge. — The princi- 

construction p} e f t h e barometer-gauge has already 

and use of r ° ° J 

the barometer- been explained. A few words will be 
guage. added here as to its use and construc- 

tion. It is always desirable to know the pressure 
in a steam boiler, as an evidence of safety, and in 
order that the fires may be regulated accordingly, 
and no more fuel be consumed than is necessary. 
Sometimes the tube containing the quicksilver is of 
glass, and then the height of the mercury can be seen. 
In other cases it is made of iron, and the change of 
level of the quicksilver is indicated by a float. 
■i- , , 216. Other steam gauges. — A ther- 

Explain the 

thermometer- mometer may be made to answer, perfectly, 
guage. ^ p Ur p 0se f a s team gauge, as is evi- 

dent from what has been said in paragraph 213. The 
advantage of such a gauge is, that it takes but little 
room ; its disadvantage, that it is liable to be broken. 
217. There is still another kind of gauge, 

Explain the . . 

principle of in which the force of the steam operates 
another guage. on a jxietallic spring, which mo ves an index 
more or less, according to the pressure. The spring 
guage is commonly used in locomotive boilers. 

Ex lain the ^^* ACTUAL PRESSURE IN DIFFERENT 

difference be- engines. — The actual pressure of steam, 

twee n high and , . , . ^ r n , 

low pressure used in different forms of the steam en- 
engmes. gine, varies very widely. There are low 



THE STEAM ENGINE. 91 

and high pressure engines. In the former, steam of 
ten to thirty pounds effective pressure is used ; in the 
latter, the pressure often reaches, and sometimes ex- 
ceeds, seventy-five pounds. To measure the pressure, 
the steam guage described in paragraph 215 would have 
to be five or six feet long. It is on account of this in- 
convenient length, that other gauges are often substi- 
tuted. 

Whatismeant 219 « B y effective pressure, is meant the 
by effective surplus over and above that which is neces- 
p ' e sary to counterbalance the pressure of the 

atmosphere, or that of the uncondensed steam, on the 
opposite side of the piston. 

Ex lain and ^®' Safety- valve. — The safety-valve 
illustrate the is a contrivance, by means of which the 
*k™afety steam finds vent through a hole in the 
valve. boiler, whenever its force becomes too great 

for safety. A piece of metal shaped ^- »\^v» qel 

somewhat like a decanter stopper, fits 
into the hole above mentioned, and is 
loaded by a weight, which can be made j||§§|^= 
greater or less at pleasure. As long as the steam has 
not too great pressure, the stopper continues in its 
place, and the boiler is as tight as if it had no such 
opening. When this pressure is exceeded, the valve is 
lifted, and steam escapes. The stopper, being loaded, 
falls back again, as soon as the pressure is relieved. 

221. The steam engine. — The power 

Explain the . . ..... 

principle of applied in the steam engine is the elastic 
the steam en- f orce f s t e am. The figure represents a 

gme, ° r 

cylinder and close fitting piston, and tubes 



92 HEAT. 

through which steam maybe admitted at pleasure, eithex 
above or below. When the valve in the 
lower tube is opened, the steam under pres- 
sure in the boiler, expands and enters the cyl- M 
inder. lifting the piston. If the steam is next 
admitted above, it drives the piston back 
again, and the latter may thus be kept in con- u, 
stant motion, and made to move wheels, 
shafts, or other machinery. It is only necessary, that 
whenever steam enters, that which is on the other side 
of the piston shall find its way out, into the air. Valves 
are provided for this purpose, which are opened and 
closed, at the right time, by the machinery which the 
piston itself moves. 

222. High pressure engine. — The en- 

Wliatisahigh 

pressure e;z- gine, here described, is called the high pres- 
91710 ' sure engine. The steam which moves it, 

must evidently have elastic force greater than that of 
the atmosphere, or it cannot expand and drive out the 
waste steam, in opposition to the elastic force of the 
air. Steam of much higher pressure is used in such 
engines, than in those to be next described, and hence 
their name. 

223. Low pressure engine. — The 

principled/ same fi S ure wil1 ar ' swer t0 illustrate the 
thelowpres- low pressure engine. The difference is, 

sure engine. , , . „ , _ . . ., . 

that the steam which has been used is 
not driven out, but disposed of, on the spot, by con- 
verting it into water. The advantage of this will 
be readily perceived. Suppose the space above the 
piston to be full of steam. A jet of water is made to 



THE STEAM ENGINE. 93 

play into it and condense the steam, and thereby pro- 
duce a vacuum. When, immediately afterward, steam 
is admitted below the piston, the latter has nothing on 
the other side to drive out, and consequently rises more 
easily. As less force is required, steam of lower pres- 
sure may be used, with a corresponding economy of 
heat and the fuel required in its producton. 

224. The condenser. — In steam en- 

use anA object § ineS > as noW made > the Water Used to COn - 

of the con- dense the steam, does not come into the 
cylinder itself, but into a side vessel, called 
the condenser. The steam expands into this vessel, and 
is condensed, producing a vacuum in the cylinder 
itself, as effectually as if the water were there intro- 
duced. The object of the modification is to avoid 
cooling the cylinder, and thereby diminish the ef- 
fect of the steam subsequently entering from the 
boiler. This engine is called the low pressure engine, 
from the fact that steam of lower pressure may be em- 
ployed to move it than is the case with the engine pre- 
viously described. It may, indeed, be made to run 
with vapor formed below 212°, instead of steam. But 
in practice, steam of from ten to thirty pounds effective 
pressure is employed. 

225. Original steam engine. — In the 
fr%inaViow original form of the steam engine, the pres- 
pressureen- sure f the atmosphere, instead of steam, 

gine. r 7 

was applied on one side of the piston, and 
it therefore received the name of the atmospheric engine. 
Suppose the cylinder in the last figure to be open at 
the top, and the piston at its full height. On condens- 



94 HEAT. 

ing the steam below it, the piston would evidently sink, 
in consequence of the pressure of the atmosphere. By 
thus employing steam pressure on one side, and atmo- 
spheric pressure on the other, a constant motion would 
be realized. But the effective power would evidently 
be less than in the low pressure engine, because part 
it would have to be expended each time in lifting 
the piston, in opposition to the pressure of the atmo- 
sphere. 

226. A test-tube provided with a pis- 

MrpUinthe tQn ma( j e of CQr j^ Qr beUer Q f WQ0( J woun & 

with cotton, suffices perfectly to illus- 
trate the scarce of power in the steam engine. On 
boiling a little water in the tube, the 
piston rises. On dipping it into cool 
water, and thus condensing the steam, 
the piston is forced down to the bot- 
tom, as in the original form of the 
low pressure engine. In the ascent 
of the piston, the analogy is not 
perfect ; for it is, in this case, the 
production of new steam, and not, as in the steam en- 
gine, the expansion of steam already produced, that 
causes the piston to ascend. 

227. Steam used expansively. — It is 

Explain the . . 

action of steam not necessary in the steam engine, that 
m the engine steam ^ ma( j e to flow from the boiler du- 

cy under. 

ring the whole movement of the piston, 
from one end of the cylinder to the other. When the 
cylinder is partly filled, the supply is cut off, and the 
steam already introduced drives the piston through thp 

1 




STEAM. 95 

remainder of the distance, by its own expansive force. 
By this arrangement, instead of using a cylinder full 
of steam at each movement of the piston, only one- 
fourth, or even less, according to its density, suf- 
fices. Steam employed in this manner is said to be 
used expansively. The term is applied especially to 
this case, although it is a fact that steam always acts 
expansively. 

228. Conversion of vapors into li- 
pZcZened Quids.— If a vapor, in any way, loses its 
into liquids ? latent heat, it at once becomes liquid. If, 

for example, steam be led into a cool pipe, 
the metal abstracts the latent heat, and the steam be- 
comes water. At the same time, the heated pipe im- 
parts warmth to the air around it. 

229. Heattng houses by steam.— 
houses heated Houses are thus heated, by steam pipes 

y s eam . passing through the various apartments. 

The pipes abstract the heat, and give it out again to the 
air of the house. The steam thus converted into wa- 
ter, runs back into the boiler to be reheated, and to start 
again on its journey. And as long as heat is supplied, 
the water continues its service as a carrier of heat. 

230. Water heated by steam. — When 

How is water 

heated by steam is led into water, the effect is the 

same as on leading it into a cold pipe. 
The water abstracts its latent heat, and becomes hot, 
while the steam itself becomes additional hot water. 
Water in different parts of a room, or even of a large 
manufacturing establishmert, may thus be made to 



96 HEAT. 

boil by one fire ; steam being led into it, by long pipes, 
from a single boiler. 

Prove that 231. PROOF THAT BOILING IS EFFECT- 

bothng isef- ED BY LATENT heat. — No amount of boiling 

fected by la- & 

ettit heat. water, if poured into cold water, will make 

it boil. But steam no hotter than the boiling water, if 
led into cold water, will have this effect. Now, as both 
the hot water and the steam were^he same in respect to 
sensible heat, if the steam effects what the water does 
not, it is evident that it must do it by hidden, or latent 
heat. It is only latent heat which the steam loses, for 
it becomes itself converted into equally hot water. 

232. Quantity of latent heat. — A 

How much la- . n ... - _ 

tent heat does pint of water will make enough steam 
steam contain? tQ fin a globe near i y f our f eet j n diameter. 

If this amount of steam could suddenly become a pint 
of water, and be prevented from flying off into steam 
again, it would become red hot. The latent heat of the 
steam would have raised the temperature from 212° to 
1212° — a thousand degrees. Steam is therefore said to 
contain 1000 degrees of latent heat. Vide App. 

233. Sum of sensible and latent 
What i* the REAT ALWAYS THE SAME . — Vapor formed 

t elation of J 

sensible to la- by the heat of summer, occupies more space, 
and contains more heat, in a latent condi- 
tion, than is contained in steam. And it is found to be 
a universal fact that, just in proportion as vapor or 
steam feds cool, or indicates a lower temperature to 
the thermometer, it contains more latent heat to the 
same quantity of water. The sum of the sensible and 
latent heat is always the same -about 1200° degrees. 



DISTILLATION. 97 

Why is there 234 ' ECONOMY IN EVAPORATION.— It foi- 

no economy in lows that evaporation at low temperatures, 

evaporating at , , . . 

low tempera- such as is practiced sometimes in sugar- 
tures? houses, has no advantage of economy. 

The vapor that passes off, carries with it less sensible 
heat, but enough more latent heat in proportion, to make 
up the difference. 

235. Distillation. — Distillation con- 

Describe the 

process of dis- sists in converting a liquid into vapor, and 
recondensing the vapor. The apparatus 
represented in the figure, 
suffices for illustration. 
Water being boiled in the 
test-tube, the steam con- 
denses in the cooler vial. 
If the latter is covered 
with wet paper, the con- 
densation is more perfect. The apparatus commonly 
used in distillation, consisting of retort and receiver, is 
represented in the appendix. 

236. Object of distillation. — The ob- 
ohject^f dis* J ect °^ distillation is commonly to purify, 
filiation? or, in other words, to separate the liquid 

distilled, from other substances with which 
it may be mixed. Thus, sea water is distilled to sepa- 
rate the pure water from salt. The water becomes 
steam, and is condensed as pure water, while the salt 
remains behind. So alcohol is distilled, or converted 
into vapor, and recondensed, to separate it from water, 
and the various refuse matters which are mixed with 
it after fermentation. But the separation is not per- 

5 




98 HEAT. 

feet, for, although alcohol is more volatile, and distils 
more rapidly, a portion of water always distils with it. 
Distilled liquors, therefore, uniformly contain a certain 
proportion of water. 



MAGNETISM. 99 

CHAPTER IV. 

ELECTRICITY ^T> MAGNETISM. 
237. Native magnets. — The native mag- 

What proper- 

ties has thena- net, or loadstone, is a mineral which has 
ivemagne . ^ remarkable property of attracting me- 
tallic iron to itself, and of taking north and south di- 
rection, when suspended and free to move. Particles 
of iron brought near, rush toward it, and remain at- 
tached to its surface, without any visible cause. It ex- 
erts this attractive force just as well through wood, 
stone, or any other material, as through the air. 

238. Artificial magnet. — The same 

Describe an . _ „ _ 

artificial mag- properties may be imparted to a piece of 
steel, by a process to be hereafter described. 
Such a piece of steel thereby becomes itself 
a magnet. Magnets are often made of a shape 
approaching that of a horse-shoe, the two 
poles being brought near to each other. A 
piece of soft iron, called an armature, is placed across 
the end to prevent the loss of magnetic power, which is 
found otherwise to occur. 

239. Magnetic needle. — If a steel bar 
magnetic nee- be made into a magnet, and then balanced 
on a pivot, it will turn, until one end points 
north and the other south. That which 
moves toward the north is called the north 
pole, and the other end the south pole. 
A small bar thus balanced is called a mag- 





100 MAGNETISM. 

netic needle, and is the essential part of the mariner's 
compass. 

240. Attraction of magnets for each 

How do the mi i r • i 

poles of mag- other. — The law of attraction between 
™achot™r? magnets is, that unlike poles attract, and 
like poles repel. The north pole of one 
magnet, therefore, attracts, and is attracted by the south 
pole of another. 

Why does the ^^" ^ HY THE MAGNETIC NEEDLE POINTS 

magnetic needle north. — The tendency of the north pole of 
pom noi t ^ magnetic needle to turn north, and the 
other pole south, may be accounted for by the supposi- 
tion of an enormous magnet running through the earth, 
with powerfully attracting poles in each hemisphere. 
In order that the pole of the supposed magnet in the 
northern hemisphere may attract the north pole of the 
magnetic needle, we must suppose it to be a south pole, 
and for a similar reason we must suppose the pole in the 
southern hemisphere a north pole. Or this inconsistency 
may be avoided, and the poles of the supposed terres- 
trial magnet named according to their geographical 
position, if we regard what is called the north pole of 
the needle, as endowed with austral or southern mag- 
netism, and the south pole with northern or boreal mag- 
netism. This view is, in fact, adopted in all writings on 
magnetism. The received theory is hereafter given. 

242. Induced magnetism. — When a 

dudioTof' piece of iron is brought near to a magnet, 

magnetism in the iron receives magnetism, by induction, 

and becomes itself, temporarily, a magnet. 

If approached to the south pole, its adjacent end ac- 



MAGNETISM. 101 

quires north, and the remote one south polarity, and 
mutual attraction results. By virtue of its ac- 
quired or induced magnetism, it will attract an- 
other piece of iron, as is represented in the figure, 
and affect it in ail respects similarly. From the 
second key, another smaller one may be sus- 
pended, and from this another, and so on. It is 
only necessary, that each successive object shall be 
smaller than the one to which it is attached. The 
magnetism thus acquired is only temporary in the case 
of iron, but in the case of steel it is in some degree 
permanent, and may, by the proper means, be rendered 
entirely so. 

243. Diamagnetism. — If a needle of 
What is said j ron ^ e hung, by a thread, between the 

of diamagnet- u J 

\sm? poles of a horse-shoe magnet, it immedi- 

ately turns, so that one of its ends points 
to the north pole, and the other to the south. This 
is also a consequence of induced magnetism, as ex- 
plained in the preceding paragraph. The metal nickel, 
oxygen gas, and many other substances, both solid, 
liquid, and gaseous, are similarly attracted by the 
poles of a magnet, though in a much less degree. All 
bodies which are not attracted are repelled, and if sus- 
pended between the poles, turn so as to bring their ex- 
tremities as far away from the poles as is possible. 
The former class are called magnetic, and the latter 
diamagnetic bodies. To show the phenomena of at- 
traction and repulsion with gases and liquids, the mate- 
rials are inclosed in tubes or bulbs. In the case of most 
substances, excepting iron, these effects can only be at- 



102 ' ELECTRICITY. 

tained by means of powerful magnets and delicate ap- 
paratus. 

ELECTRICITY. 
244. Frictional electricity. — If a 

\vhflt is T7"tC" 

tionai electri- glass tube is rubbed with silk, it will after- 
^y - ward attract to itself filaments of the silk, 

as a magnet attracts iron. Or, if the knuckle be ap- 
proached to the tube, a spark may be drawn from it. 
These phenomena are called electrical. Both glass and 
silk are said to be electrically excited. The same ex- 
periment may be made with a stick of sealing-wax. 

State the theory 245. THEORY OF ELECTRICITY. AcCOrd- 

of electricity. j n g to ^ e v i ew commonly entertained of 
these phenomena, both glass and silk contain two electri- 
cal fluids in a state of combination, which are so sepa- 
rated by friction, that the positive fluid of both ac- 
cumulates in the glass, and the negative in the silk. 
The positive sustains the same relation to the negative, 
that the north polarity of a magnet does to the south ; 
and, in consequence of the difference of the separated 
fluids, the two bodies containing them attract like op- 
posite poles of a magnet. It is also true, that similarly 
electrified bodies repel like similar poles of magnets. 
As in the case of heat and light, we know nothing of 
the electrical fluid, save by its effects. 
Illustrate by 246. The human body may also be elec- 

exampies. tricially excited, so as to yield a spark, by 

rapid sliding over a carpet. Gas may be lighted by the 
spark. The gas in certain manufactories is instantane- 



GALVANIC ELECTRICITY. 103 

ously lighted throughout the whole establishment by 
electricity developed by the friction of the machinery. 

247. Conduction of electricity. — Like 

Explain the . . 

conduction of heat or caloric, electricity may be conducted 
,xlty ' from one body to another. Thus, if a piece 
of metal be electrically excited, or, in other words, 
charged with a quantity of either the positive or nega- 
tive fluid, another piece of metal will immediately be- 
come so on connecting it with the first by a metallic 
wire. The connection being formed, it will attract or 
repel filaments of silk or other material, precisely as the 
first one does. The fluid is supposed to flow from one 
piece of metal to the other, through the wire, and we 
therefore speak of a current of electricity. But it is 
not certain that any thing actually passes, any more 
than in the case of light and heat before considered. 

248. Galvanic electricity. — It is also 

What is gal- 
vanic electri- found that electricity is developed when 

Cl y ' two metals are placed in contact with each 

other, and with an acid at the same time, 
as is represented in the figure. The metals 
must be such that the acid will act on one 
of them. Zinc and copper being used 
the former is dissolved, and the cur- 
rent flows continuously in the direction 
indicated by the arrows. This apparatus is the sim- 
plest form of the galvanic battery. 
wi „* ;* ™ 249. Electrodes. — For convenience in 

What is an 

electrode t certain experiments, it is customary to at- 
tach platinum wires, to the exterior portions of the me- 
tallic slips. These are called electrodes. The wire con- 




104 GALVANIC ELECTRICITY. 

neeted with the copper forms the positive electrode, and 
the one attached to the zinc, the negative. 

250. Platinum wire is chosen, because 

Wh '/ is plati- , . 

nvm used for there is frequent occasion to immerse the 
electrodes ? electrodes in corrosive liquids, and this me- 
tal, for the most part, withstands their action. For 
many experiments, it is found best to flatten the ends 
of the wires forming the electrodes, so as to produce 
a larger surface. The same object may also b« effected 
by terminating them with strips, of platinum. 

251. Electrical condition of atoms. 

What is the . . 

electrical con- All atoms of matter are regarded as origi- 
d Tms^ nally charged with either positive or nega- 

tive electricity. Hydrogen and the metals 
are electro-positive ; oxygen, chlorine, and cyanogen 
and other substances, to be described hereafter, are ne- 
gative. A molecule of water is made up of a positive 
atom of hydrogen, and a negative atom of oxygen ; 
hydrochloric acid, of positive hydrogen and negative 
chlorine ; oxide of silver, of positive silver and nega- 
tive oxygen. The figure, in which + represents suyx\ 
positive and — negative, may represent a mole- ^^ 
cule of either of the compounds named. 

252. Quantity of electricity. — The 

What quanti- . 

ty of electrici- quantity of electricity thus combined or 
t y is contained neTltra ii ze d, in almost all kinds of matter, 

in water ? > > 

is enormous. Faraday has shown that 
a drop of water, contains more than is discharged in 
the most violent flash of lightning. 

The terms atom, and molecule, are synonymous. But "molecule" ii 
limited, in the present work, to the particle of a compound. 



GALVANIC ELECTRICITY. 



105 




253. Decomposition of water. — If the 

Describe the . 

decomposition electrodes are immersed in water, as repre- 
of water. gented m the figure, the 

water is decomposed, and separated 
into its elements. Bubbles of hydro- 
gen collect on the negative electrode, 
and bubbles of oxygen on the posi- 
tive, and finally disengage themselves, 
and rise through the water. 

254. It is to be observed that positive 

Why does hy- _ .. . , .. , . . . 

drogen appear hydrogen is liberated at the negative pole, 
atthenega- as jf fae latter had a power analogous to 

tive pole f r o 

that of the magnet for iron, to draw the 
hydrogen out of the water, in which it exists combined. 
On the other hand, negative oxygen is liberated at the 
positive pole, as though the latter had the same attrac- 
tive power for oxygen. The above figure is given 
solely for the purpose of illustration. The actual form 
of apparatus for decomposing water, by the galvanic 
current, is described in a subsequent paragraph. 

255. Theory of the decomposition of 

Give the theo~ 

ry of the de- water. — It is a remarkable circumstance, 
composition of in the decomposition just described, that it 

water. r J 

continues to occur even when the elec- 
trodes are quite widely separated from each other. Now, 
a molecule of water is extremely 
small, and cannot occupy the space 
between the electrodes, if they are 
separated to any considerable ex- 
tent. The space must be occu- 
pied by many such particles, which, 
5* 




106 GALVANIC ELECTRICITY. 

for the sake of definiteness, we will conceive of as Ar- 
ranged in straight lines, between the two electrodes. 
The circles in the figure, inscribed H and O, represent 
one of these lines of molecules. The difficulty now 
arises, to account for the fact, that when the hydrogen is 
liberated at the negative pole, the oxygen, combined 
with it a moment before, is not also liberated at the same 
point. The view to be taken of it is as follows : that as 
soon as the atom of oxygen loses its hydrogen, it combines 
with the hydrogen of the next molecule of water. 
The oxygen of this second one being thereby liberated, 
combines with the hydrogen of the next ; and this 
decomposition and recomposition continues throughout 
the series. The end of the series being reached, the 
last oxygen atom escapes in the form of gas. The action 
being simultaneous throughout the series, this evolution 
occurs at the instant that the hydrogen is set at 
liberty at the negative electrode. It is, therefore, 
quite as proper to give the explanation of the diffi- 
culty first stated, by beginning with the liberation of 
oxygen at the positive electrode. We tliea suppose the 
hydrogen to combine with the oxygen of the next 
molecule of water in the series, and so on to the nega- 
tive electrode, where hydrogen is evolved. The ac 
tion is, in fact, as before stated, simultaneous. 

256. Deposition of metals. — The me- 

Explain the . . ^ , , 

deposition of tals are electro-positive. Oxygen, chlorine 

metals by gal- & Qn the Qther han( j are neg ative. If 

therefore, oxides, chlorides, or cyanides 
of the metals are subjected to the action of the 
electrodes, they are decomposed, while the metal 



ELECTRO-PI ATING. 107 

goes to the negative, and the oxygen, chlorine, or 
cyanogen, to the positive. But the metals, when sepa- 
rated from their combinations, being solid bodies, can- 
not escape. They collect on the negative electrode, in- 
stead. If this be attached to a brass spoon or fork, or 
any other object it is desired to plate, the spoon be- 
comes itself the electrode, and the metal is deposited 
upon it as long as the action of the battery continues. 
At the same time, the oxygen, or other negative ele- 
ment, goes to the positive electrode, generally cor 
roding it, instead of passing off as gas. 

257 . Silvering apparatus. — The re- 

What appara- . 

tue is required quirements for electro-silvermg or gilding, 

f Zin 9 T°' 8il ' are first > a batter y of somewhat different 
form from that already described, though 
precisely the same in principle : second, an acid to ex- 
cite it ; and third, a solution containing gold or silver. 
These will be described in turn. 

258. A convenient form of the ^^^^^^ 

apparatus is represented in the fig- v ^^\f~^ \ gi rl~Sl§} 
ure, and may be prepared from »iH|f 
sheet zinc and copper in a few mo- jftf "j lffSiL '- 
ments. It consists of a bent strip 

of the former metal, with a strip of copper 
Explain the f as t e ned between the two portions. The 

figure. r 

metals should be within an eighth of an 
inch of each other, but without contact. To secure 
this, they are tied together with thread, bits of wood or 
cotton cloth being previously interposed. Copper 
wires being attached to the zinc and copper, as rep- 
resented in the figure, the apparatus is placed in a com- 
mon tumbler, and the battery is complete. 



108 GALVANIC ELECTRICITY. 

, . 259. Before combining the battery as 

How and why ■ ° J 

is the zinc above described, it is best to wash the 

$ck££f zinc with soa P and water > and afterward 
with dilute sulphuric acid, and then to 
immerse it for half a minute or so in a solution of ni- 
trate of mercury. By this process, the zinc acquires 
a thin film of quicksilver, which afterward protects it 
from the action of the acid used to excite the battery, 
excepting when the circuit is completed. When the 
battery is in operation, it also has the effect of making 
the action, more equal and constant. It is then to 
be again washed, and newly immersed in the acid solu- 
tion. This solution is prepared by dissolving quicksil- 
ver, of the bulk of two peas, in nitric acid, and pouring 
the clear liquid into a tumbler of water. 
_ . , 260. The exciting acid. — The exci- 

how is the ex- . . . . . 

citing acid ting liquid is dilute sulphuric acid, consist- 
pr.par ^^ o £ one ^^ o ^ ^ vitriol, to ten parts of 

water. The acid is mixed with the proper quantity of 
water and set aside to cool. 

261. The silvering solution. — To 

How is the sil- . . 

vcring solution make a half pint of the solution, a dime is 
prepared? placed in a test-tube and dissolved in ni- 
tric acid, the solution being diluted with water. Muri- 
atic acid is then added, which precipitates the silver, in 
the form of a white curd. This is allowed to settle, and 
the green liquid, which contains the copper of the coin, 
is poured off. Water is again added, and the curd al- 
lowed to settle ; this cleansing process is several 
times repeated. The test-tube is then half filled with 
water, and heated, and bits of cyanide of potassium ad- 
ded, until a transparent solution is obtained. 



ELECTRO-PLATING. 109 

262. A solution for gilding, is prepared 

How is the so- . . . ., , 

'utionfor by drying a solution 01 gold, at a moderate 

r iteJ 9 ? pr€ ~ ^eat, an( * dissolving ^ i n cyanide of po- 
tassium, as above described. The process 
for gilding, is in all respects the same as that for the 
deposition of silver. 

263. The process. — The battery and 

How is the sil- . 

vering process silvering solution being prepared, the cop- 
conducted? per coin, or other object to be silvered, is 
cleansed with potash, rubbed with chalk or rotten- 
stone, and then attached to the wire proceeding from 
the zinc. A silver coin is fastened to the other wire, 
and immersed in the silvering solution ; acid is then 
added to excite the battery, and the object to be silvered 
is lastly immersed. It should be hung face to face with 
the silver coin, and quite near to it, the two being kept 
in their places by blocks placed across the tumbler, as 
represen^cfin the figure. The coin will receive a per- 
ceptible coating within a few minutes, and will be more 
thickly covered, according to the time of immersion. 
The deposit is hastened by keeping the solution mode- 
rately warm. This is especially advantageous in the 
commencement of the process. The newly plated sur- 
face is without lustre, and requires burnishing after re- 
moval from the solution. 

264. Object of the silver coin. — The 

What is the 

object of the piece of silver is attached to the positive 
0171 ' wire, to maintain the strength of the solu- 
tion. It is eaten away, and dissolved as fast as silver 
is deposited on the objects connected with the negative 
wire. The reason of this is, that the cyanogen of the 



110 GALVANIC ELECTRICITY. 

solution, when it goes to the positive pole, as before ex- 
plained, combines with silver, forming new cyanide of 
silver, which dissolves and mixes with the rest. Thus, 
the strength of the solution is always maintained. The 
coin is attached to the negative wire, by flattening the 
latter, laying it on the back of the coin, and covering 
the whole with sealing wax ; the coin and wire should 
be previously slightly warmed, and the wax used at a 
moderate heat, so that it shall not run between the wire 
and the coin, and prevent their perfect contact. 

How are med- 265. COPYING OF MEDALS. If it is de- 

ah copied? sired to copy the face of a medal or a coin, 
the same apparatus suffices. The reverse and edges of 
the coin are very slightly oiled, to prevent the adhesion 
of the copy about to be made. It is then placed in the 
solution. The metal deposits upon it, copying perfectly 
every elevation and depression. When the crust is suffi- 
ciently thick, which will be after the lapse of twelv^ 
hours, the coin, with its shell of metal, is removed, and 
the whole process repeated with the mould. The de- 
posit which now forms in the shell, is an exact copy of 
the face of the original coin. Moulds are also made by 
stamping the coin into soft metal, and using the impres- 
sion thus produced instead of the copper shell. Copper 
plates, for engravings, may be copied so perfectly by 
the first method, as to be fully equal to the original. 

How are wood 266. COPYING OF WOOD CUTS. The diffi- 

cuts copied? culty of copying other than metallic ob- 
jects, by the processes, that they are not generally good 
conductors. Thus, when a wood cut is attached to 
the negative wire, it does not itself receive a nega- 



ELECTRIC LIGHT. 



Ill 



tive character from the wire, and will not, therefore, 
take positive metal from the solution. This is obvia- 
ted by covering the block with a fine powder of plum- 
bago or black lead, which has good conducting power. 
. B 267. This process is very extensively 

It what cdS6s 

is the process practised. Where a large number of cuts 
practised . Q f ^ same j^nd are wanted, as for exam- 
ple, to print labels for dry goods, only one engraving 
on wood is made, and numerous copies are t iken by 
the above process, which is much less costly. 

268. Heating effects of v he cur- 

Describe the 

heating effect rent. — If the electrodes are connected 
of the current? whfle the b attery j s m actl on, the wire be- 
comes heated more or less strongly, according to the 
size of the plates. If the plates are very large, the 
wire melts, even though it be of platinum, the most 
infusible of metals. Gold may even be converted in- 
to vapor by the same means. Carbon, supposed a few 
years since to be entirely infusible, may be also super- 
ficially fused, and even volatalized between the electro- 
des. It condenses again at a little distance, in the form 
of microscopic crystals. Imperfect diamonds have been 
thus artificially produced. With such a battery as 
has been described the elevation of temperature would 
be scarcely perceptible. 

269. The electric light. — If the current 

How is the . 

electric light be allowed to pass between two points of 
produced? prepared charcoal, an exceedingly intense 
light is produced, accompanied by great heat. Char- 
coal is employed because it is a comparatively infu- 
sible, and inferior in conducting power. A metallic 



112 GAI VANIC ELECTRICITY. 

wire, under the same circumstances, would melt, or if 
too large to undergo fusion, would allow the current to 
flow readily through it, without that detention which is 
essential to the production of the above effects, in their 
highest degree. 
TT . _ 270. If the charcoal points be with- 

How is the *■ 

electric flame drawn from each other, a splendid electric 
produced? flame is produced between them. This 

flame is not the result of combustion, for the char- 
coal is extremely dense, and wastes away but slow- 
ly. It is purely electric. Metals melt in it, and are 
dissipated in vapor. A much larger battery than that 
just described, is requisite for the production of ei- 
ther the light or flame. In experimenting with the 
compound battery, hereafter described, a slight %park 
will be observed, on separating the electrodes. 

271. Source of galvanic power. — The 

What is the ... n, ,-, -. . . . 

cause of the gal- exciting cause of the galvanic current is 
panic current? found in the chemical action which occurs 

Explain the che- ' . _ 

mical action. m the battery, lhis action is analagous to 
that described in § 255. Suppose, for 
example, the acid with which the zinc and copper are 
in contact, to be hydrochloric, each molecule of 
which is composed of an atom of hydrogen and 
an atom of chlorine. The zinc becomes positive 
where it is in contact with the acid, and negative at 
the other end, the extremities assuming different states, 
as in the case of a piece of soft iron suspended from a 
magnet. The outer portion of the copper being in con- 
tact with the negative end of the zinc, is, itself, nega- 
tive, while the end immersed is positive. The atoms 



GALVANIC ELECTRICITY. 113 

composing the acid, are supposed to be arranged as rep- 
resented in the figure. The alternation of positive and 
negative, in copper, zinc, and the line of acid molecules 
is analogous to the case of the sus- <^ 

pended keys. As long as the metals ^ — Jj^V — -^ 
are immersed, and made to touch, an ^k^^m^\ ^jjjl3 
atom of zinc constantly combines 1 JJ Jjjh liiiBW 
with an adjacent atom of chlorine. \| S~ -O 
It follows, that no chlorine is set at |;llM^^ ;;; ^A l| 
liberty. As fast as each atom unites ] ^^^S^M^^ 
with the zinc, its hydrogen combines ' 

with the next chlorine, the hydrogen of this, with 
the next, and so on, as before explained, in the de- 
composition of water. Hydrogen is therefore con- 
stantly given off at the surface of the copper. But 
when the two metals are not in contact above the li- 
quid, and the circuit is, consequently, not completed, 
there is no negative influence exerted at the extremity 
of the copper, and the series of decompositions, before 
described, does not occur. 

„ 7 272. A SALT EMPLOYED AS EXCITANT 

Explain how . . 

a battery can It is not essential, that an acid shall be used 
asattT d hy as the excitin g liquid in the galvanic bat- 
tery. A metallic salt is sometimes em- 
ployed. This may be best illustrated, by supposing 
chloride of copper to be employed instead of hydrochlo- 
ric acid, which is chloride of hydrogen. The chlo- 
rine goes to the zinc, as in the previous case, and the 
copper of the salt, to the strip of copper, placed in the 
solution. Being a solid, it remains there, and en- 
crusts the copper, instead of being evolved, as in the 
case of hydrogen. 



114 



GALVANIC ELECTRICITY. 



273. Different kinds of batteries.— 

What is said 

of the differ- There are different kinds of galvanic bat- 
tltteries^' teries, but the principle in all is the same. 
Two of the forms in most common use 
are described in the Appendix. Smee's battery is 
especially recommended to the student, for its cheap- 
ness, simplicity, and efficiency. It is very similar, as 
will be seen, to the simple one which has been already 
described. 




2/4. Compound circuit. — For the sake 

What is said '/..,.. i, i /• • n 

of the com- oi simplicity, all the foregoing decomposi- 
pound circuit? t i on s have been described, as a result of the 
action of a simple voltaic circle, consisting of an acid, 
and two metals. But, it is found that in many decom- 
positions, the power of such a battery is insufficient. 
The efficiency is increased by employing several single 
batteries together, and bringing them all to bear upon 
the same electrode. 

How are heat- 275. The heating and magnetic effects 
%ng and mag- Q f ^ battery are very much increased by 

netic effects . 

produced? uniting the plates, as in the preceding fig- 
ure, where all the zinc plates are joined together, so as 
virtually to form one. The quantity of the current is 
thus increased. Power of decomposition, and to give 
shocks, such as are taken from an electrical machine, 



GALVANIC ELECTRICITY. 



115 



are increased by uniting them as in the figure which 
follows. The intensity of the current is thus increased. 




What is the 
meaning of in- 
tensity $ Of 
quantity ? 



276. Meaning of intensity and quan- 
tity. — The terms intensity and quantity 
are rather vaguely used, and do not de- 
scribe as definitely as may be desired, the 
different properties of the current. The student must 
associate the term quantity with increased heating and 
magnetic effects, and the term intensity, with power 
of decomposition. 
_ f , 277. Decomposition by the compound 

Explain the 

apparatus for circuit. — For the decomposition of water, 

tfZl°r Ui0n a SerieS ° f six CU P S > 3 Uch as haVe been a1- 
ready described for use in plating, will suf- 
fice. They are to be united according to the second ar- 
rangement. The zinc of each cup is to be connected with 
the copper of the next in order, by a copper wire, forming 
a good metallic contact. This being done, another long 
wire is fastened to the first copper plate, and one, also, to 
the last zinc, and bits of platinum wire or foil are attached 
to their ends. A small test-tube is then filled 
with acidulated water, and inverted in a cup, 
also containing water and acid. The wires 
are bent upward into the cup, as represented 
in the figure. The battery being now set in 
operation, by dilute acid, as before described, 




116 GALVANIC ELECTRICITY. 

the evolution of gas immediately commences from the 
the platinum wires. This compound battery will be 
found rather slow in its operation, and has been de- 
scribed only for the purpose of illustrating the use of 
the more powerful galvanic batteries of similar con- 
struction. The student is advised to substitute for it 
•the Voltaic pile, hereafter described. 

278. An explosive mixture. — A mix- 

What proper- . - 

ty has the ture or hydrogen and oxygen gases, in the 
mixture thu* proportion in which they are here evolved. 

produced? . . . 

is explosive. This property is one evi- 
dence that the mixture actually consists of oxygen 
and hydrogen. A sufficient quantity being col- 
lected, the mouth of the tube is covered with the finger, 
the tube inverted, and a match applied at the mouth. 
A slight puff is all the evidence that will be obtained 
from a small quantity of the mixture. A test-tube full 
will give a sharp report. 

279. Separate collection of the 
How may the _. . 

gases be col- gases. — By using two test-tubes, instead 
lectedsepa- Q f ag k e f ore described, and introduc- 

rately ? . . 

ing an electrode into each, the gases may 
be separately collected and tested by the methods given 
in the section which treats of those gases. 

280. The water is acidulated in the ex- 
waterto be de- periment, to make it a better conductor of 
composed t ^ e influence which must pass through it 

acidulated? r ° 

from one electrode to the other, in order 
that the decomposition may take place. The reason 
for using platinum electrodes has already been given. 
In the present case, if the copper wires themselves 



GALVANIC ELECTRICITY. 117 

were introduced, the negative electrode would appro- 
priate all the oxygen to itself, thereby becoming gradu- 
ally converted into oxide of copper, which would dis- 
solve, and nothing but hydrogen gas would be obtained. 
281. Decomposition of a salt. — The 
Describe the decomposition effected by the galvanic 

decomposition x jo 

of a salt. current, may be more strikingly illustrated 

by introducing the electrodes into a dilute 

solution of sal-ammoniac, previously 

colored by litmus, or red cabbage. Jm 

BT71 
Chlorine is liberated at the positive 

pole, and bleaches the solution in its Jj|| 
vicinity, while ammonia is evolved ^My 
with hydrogen, at the negative pole, 
and changes the color of the solution from blue to red. 
That of the cabbage is changed by the same means, 
from red to green. By employing a glass box with two 
compartments, such as is represented in the figure, the 
two portions of the liquid may be kept distinct. It is 
essential, for reasons that will be understood from the 
preceding paragraph, that there be an unbroken chain 
of molecules of the electrolyte, or substance to be de- 
composed, between the electrodes. This is effected by 
making the partition quite loose, and keeping it in its 
place by strips of paper, placed along the edge. All the 
communication that is essential, then takes place through 
the pores of the paper, while the partition at the same 
time prevents the mixing of the contents of the sepa- 
rate cells. The same object may be accomplished by 
the employment of two tea-cups, holding the liquids,. 
and connected by moistened lamp-wick ; a larger pile, 




118 GALVaNTC electricity. 

and a longer time, is in this case required to effect the 
decomposition. The glass box may be made according 
to the directions given in paragraph 33 for making a 
prism. 

Describe the 282. The VOLTAIC PILE. The first 

Voltaic pile, form of galvanic battery ever produced is 
represented in the figure, and is called the 
Voltaic pile, from the name of its inventor. 
It consists of a succession of discs of zinc, 
copper, and cloth, moistened with acid, al- 
ternating with each other, as represented 
in the figure. Each series forms a simple 
battery, and the whole pile is a compound Ij- j^sb z: 
battery, essentially the same as that before 
described. Wires to serve as electrodes are to be at- 
tached to the extreme copper and zinc. 

283. The enlarged form of the Voltaic 
of the en- pile represented in the next figure will be 
l< Uef Voltaic found a most efficient apparatus for ef- 
fecting decomposition. It is composed of 
sixteen plates of each metal, each having a surface 
of twelve square inches. The zinc should bo amalga.- 
mated, as before explained. Flannel, or any similar 
material may be employed to separate the plates. With 
this piece of apparatus, the spark is readily obtained, and 
slight shocks may be taken by bringing the two hands 
into contact at the same moment 
with the top and bottom of the pile. 
On terminating the electrodes with 
fine iron wire, and frequently uni- 
ting and separating them, scintil- 




ELECTRO-MAGNETISM. 1 19 

lations of the burning metal may also be readily pro- 
duced. By increasing the number of the plates still 
more striking effects are obtained. With a pile con- 
sisting of six or eight plates a foot square, platinum 
wire connecting the electrodes may be readily fused. 
Such a battery is also more effectual in the electro- 
magnetic experiments which follow. 

Describe the 284. MAGNETIC PROPERTIES OF THE CUR- 

magnetic pro- RENT# — jf the wire connecting the zinc 

perlies of the # ° 

galvanic cur- and copper of the galvanic battery be wound 
in a spiral, as represented in the figure, the 
coil, or helix, as it is termed, be- 
comes possessed of magnetic 
properties. Like a magnet, it attracts iron, and other 
magnets, and according to the same laws. 
How may a 285. The suspended bar. — A rod of iron 

rod of iron be brought near one of the extremities of the 

suspended in ° 

the air? coil, is not only attracted, but actually 

lifted up into the centre of the coil, where it re- 
mains suspended without contact, or visible sup- 
port, as long as the battery continues in action. 
Science has thus realized the fable of Mahomet's 
coffin, which was said to have been miraculously 
suspended in the air. The helix, for this and 
similar experiments, is wound closer than is rep- 
resented in the figure, and is composed of several 
layers of wire. A powerful battery is also essential to 
success in this experiment. 

286. Polarity of the coil. — That 

What is the . 

action of a such a coil has polarity, may be proved, 
it attracts the north pole of a magnet, and 



120 



OALVANIC ELECTIUC1TY. 




is therefore a south pole. The other end 
attracts the south pole of a magnetic nee- 
dle, and is therefore, itself, a north pole- 
But the direction in which the current 
moves round in the helix, determines 
which shall be north, and which south. 
As the current is represented to move 
in the first of the two coils in the figure, the up- 
per end of the coil is north, and the lower end south. 
If it is made to move in the other direction, as in 
the second figure, the poles are reversed. 

287. Consequent motion of a stts- 

How may we 

obtain motion pended coil. — To obtain motion of the 
°Llf. eC0% %U co ^ i tse lf? as a consequence of its magne- 
tism, it is necessary to suspend it ; and in 
order to suspend it with perfect freedom of motion, it is 
necessary to suspend the battery 
with it. Such a suspended coil 
and battery is represented in the 
figure. In preparing it, the wire 
is wound forty or fifty times 
round a test-tube, (which is afterward removed,) and 
copper and zinc plates then attached to the ends. 
The plates are tied together with several layers of paper 
between them, then dipped in acid, and the apparatus 
carefully suspended by an untwisted silk fibre. The 
acid absorbed by the paper, suffices to maintain for 
some time the action of the battery. On approaching 
a magnet to either pole of the suspended coil, it is at- 
tracted or repelled precisely as if it were a magnet. In- 
stead of suspending the apparatus by a thread, it may 




ELECTRO-MAGNETISM. 121 

be floated on acidulated water, by means of a cork, 
and submitted to the same experiment. In this con- 
struction, the wires proceeding from the end of the 
coil, pass through the cork, before connecting with the 
metallic plates. The first described method of suspen- 
sion is regarded as the best. 

288. The coil a magnetic needle. — 

How may the . • 

coil be conver- On floating a coil with extreme deli- 
nt^VdleT cac Y u P° n water > and Protecting it from 
all currents of air and water, it assumes 
north and south direction, and becomes, in fact, a mag- 
netic needle. This can only be accomplished by 
means of a light glass cup, blown for the especial pur- 
pose, and prolonged into a cone below, to give it stead- 
iness in the water. This cup is filled with dilute acid, 
in which the plates are immersed, and is then floated 
in a larger vessel. 

289. Mutual action of coils. — Two 

Describe the 

mutual action helices, or coils, such as are described in 
°coiu agni *h& ^ ast P ara g ra ph, floating near each other, 

attract or repel, precisely as if they were 
magnets, according as like or unlike poles are brought 
together. They finally attach themselves to each 
other in the position represented in /~v 
the figure, lying parallel and with W 
opposite poles in contact. In this ^J 
position, it will be observed, that at the point of con- 
tact, the currents are moving in the same direction, 
The attraction of the unlike poles, may be regarded, 
then, as a consequence of the attraction of like cur- 
rents. For it is found to be universally true, that 

6 




122 



GALVANIC ELECTRICITY. 



currents moving in the same general direction, attract 
each other, while those moving in opposite directions, 
repel. 

What is the 290. MUTUAL ACTION OF COIL AND MAG- 

mutual action NET — jf a floating magnet be substituted 

of a coil and ° ° 

magnet? for one of the coils, in the above ex- 

periment, the result is not in the least affected. 
They act toward each other precisely as if both 
were magnets, or both, coils. 

291. Action of a single wire on 

What is the . , . 

action of sin- a coil.— A single wire, carrying a cur- 

gle wire on a rent actg Qn & fl oa |;i n g co fl j n fa e same 

magnetic coil s 1 D 

manner. Stretched above it, as in- 
dicated in the figure, the north pole of the coil 
will move to the right. The motion is such as to bring 
adjacent currents, in the wire, and in the coil, to co- 
incide in direction. 

292. Polarity of the coil imparted 
has the mag- to iron. — A bar of soft iron placed in 
no.ticcoil upon t k e c0 [\ becomes itself a magnet, and re- 

metalsf 7 ° 

ceives the name of electro-magnet. It 
should be wound with several layers of eontin- ^ 
nous wire, the latter being covered with cotton, §4--' 
to prevent any lateral passage of the current. 
The horse-shoe shape, in which the poles are 
brought round near to each other, is the more 
common. The power of such magnets contin-" 
tinues only while the current is passing. Electro- p 
magnets have been constructed capable of lifting a ton^ 
or even more. They are sometimes employed in dress- 
ing iron ores, to separate, by their attraction, the work- 






ELECTRO-MAGNETISM. 123 

able ore from the refuse earth with which it is mixed. 
A steel bar introduced into the helix while the current 
is passing, becomes permanently magnetic. Permanent 
magnets, are now commonly made in this manner. 

293. Permanent magnetism of steel. 

What effect 

has the mag- It appears, from the last paragraph, that 

njlic coil upon ft bar of soft ^ | g & magnetj as l ong as 

an electrical current circulates around it, 
But the steel, if once magnetic, remains so permanent- 
ly. This is accounted for, by supposing that the cur- 
rent, in the wire, excites a current in the surface of the 
steel itself, which continues to flow, without interrup- 
tion, after the wire is removed. 

294. Action of a single wire on 

What is the 

action of a a magnet. — A wire, carrying a cur- 
tS^HSTi ° n rent in the direction shown in the 

a magnet f 

figure, acts on a magnet, precisely as 
on a floating coil. The north pole of the mag- 
net is made to deviate to the east. The mo- 
tion is such as to bring adjacent currents in wire 
and magnet to coincide. 

295. Electrical theory of mag- 

Explain the 

electrical theo- netism. — According to this theory, all mag- 
r tism? ma9ne ~ netism, including that of the load-stone, 
the magnetic needle, and that of the earth 
itself, is a consequence of the circulation of electrical 
currents. In the earth, such currents are known to be 
excited, and kept in motion, by the sun, heating in turn 
successive portions of its surface. They flow from 
east to west, making of the earth, as it were, an im- 
mense coil, or helix. In magnets they are also in con- 



124 



GALVANIC ELECTRICITY. 



Explain the 
figure. 



slant circulation, the direction being dependent on the 
position in which the magnet is held. In the case of 
a magnet whose north pole is directed north, the di- 
rection is from west to east across the upper surface, 
and of course, in the contrary direction on the under 
side. The earth acts on a magnet, or a floating coil, 
as one helix acts on another. The north and south 
direction of the magnetic needle is a consequence of 
this action. 

296. The theory illustrated. — In 
illustration of this theory, let a globe be 
coiled with a wire, carrying a current, as indicated in 
the figure. Let the current flow from east to west 
through the coil. A small magnetic needle placed at 
different points on the surface 
of the globe, however the po- 
sition of the latter may be 
changed, will always point to 
its north pole. It is under- 
stood, in this experiment, that 
the current is strong enough 
to overcome the influence of 
the earth itself on the mag- 
net. A freely movable coil through which a current 
was passing, would, in this case also, act precisely like 
a magnet. 

297. Magnetic telegraph. — The ex- 
planation of the mechanism of the mag- 
netic telegraph belongs to Natural Philoso- 
phy. The principle of its operation may 




Explain the 
principle of 
the magnetic 
telegraph 



MAGNETIC TELEGRAPH. 



125 



be here given. It has already been stated, that a piece 
of soft iron becomes a magnet, when a current of elec- 
tricity circulates in a coil surrounding it. Now. sup- 
pose the two ends of such a coil, situated in a distant 
city, to be made long enough to reach a battery in 
the place where the reader resides, and to be stretched 
along over posts, and connected with the poles of the 
battery. The current occupies no perceptible time in 
its passage. Therefore, as soon as the battery is set 
in operation, it circulates through the whole extent 
of the wire, and, of course, through the coil in the 
distant city. The piece of iron which it incloses 
is made a magnet, and will immdiately lift its arma- 
ture. If the current is stopped, the piece of iron ceases 
to be a magnet, and drops its armature. But the 
operator at the battery can send or stop the current at 
will, by simply disconnecting one of the wires, and 
.thereby lift or let fall the armature a hundred or a thou- 
sand miles off, as often as he pleases. He can have 
an understanding, also, with the person in the distant 
city, who sees the motion of the armature, as to what 
it shall mean. One lift may indicate the letter A ; two 
lifts, the letter B ; and so on. Words may be similarly 
spelled out, and it thus becomes possible to commu- 
nicate ideas by electricity. If these lifts of the arma- 
ture can be made to record themselves on a slip of 
paper, the further advantage of writing at the distant 
station is gained. And this is precisely what is realized 
i:i Morse's telegraph, and more particularly described in 
all recent works on Natural Philosophy. 



126 galvanic electricity. 

298. The earth, used as a conductor. 

What ts said 

of the earth It would seem requisite to extend both ends 
a&a^conduc- of the wire f orming the coil through all 

the intervening distance, and then to con- 
nect them with the opposite poles of the battery ; but 
it is found, in practice, that one is sufficient, and that 
all the middle portion of the second wire may be dis- 
pensed with. The remaining ends, one connected 
with the helix, and the other with the battery, being 
made to terminate in large plates, and buried in the 
ground, the earth between them is found to take the 
place of the second wire, and complete the circuit. 

Mention some 299. APPLICATIONS OF THE TELEGRAPH. 

remarkable There are many applications of the tele- 

apphcahons 

of the tele- graph beside the one of transmitting mtel- 
graph. ligence to distant places. In the city of 

Boston, an alarm of fire is instantaneously communi- 
cated throughout the city, and the bells rung by tele- 
graphic apparatus. 

In Marseilles, France, a single clock is made by sim- 
ilar means to indicate the time on dials, placed in the 
street lamps of the city. Electro-magnetic apparatus 
has also been employed with the most remarkable suc- 
cess in increasing the dispatch and accuracy of astro- 
nomical observations ; making it possible to accomplish 
during a single night in the study of the heavens, what 
formerly cost a month of labor. 

300. Physiological effects of gal- 

Describe the ._. . P . , 

physiological vanism. — The nerves of animals are ex- 
effects of gal- t reme iy susceptible to the galvanic influ- 

vanism? J r ° . 

ence. The apparatus represented in the 



PHYSIOLOGICAL EFFECTS. 127 

figure, which consists of strips of zinc and copper, 
three inches in length, separated by a cork, is sufficient 
to produce convulsive twitchings 
in the legs of a frog or toad, 
larger apparatus produces more decided effects. The 
legs are to be employed, with a portion of the back 
bone attached, which is grasped by the sharpened ex- 
tremities of the galvanic tweezers. As often as the 
circuit is completed, by bringing the other extreme ties 
into contact, by the pressure of the fingers, the legs 
are observed to twitch, as if they were still possessed 
of life. The leg of a grasshopper, held in its 
thickest part, may also be employed in the experiment. 
In both these cases, the moisture of the flesh or skin 
is the exciting fluid of the galvanic pair. In view of 
the destruction of life which they involve, these expe- 
riments should be confined to the lecture room, or only 
made where many persons are to be instructed by their 
exhibition. 

301. Discovery of galvanism. — In the 

How was the „ „ . * • ■ i -i • 

discovery of words of Arago, " this immortal discovery 
galvanism arose in the most immediate and direct 

made f 

manner, from an indisposition with which 
a Bolognese lady was affected, in 1790, for which hei 
medical adviser prescribed frog broth." The frogs had 
been killed and skinned, and were lying on the table 
of her husband's laboratory. Experiments were in 
progress with an electrical machine, which stood near 
them, when it was observed that the frogs' legs were 
convulsed, as the spark passed. This was not a new 
fact, but Galvani was not acquainted with it, and un- 



128 GALVANIC ELECTRICITY. 

dertook to find out the cause. In preparing for the in- 
vestigation, he chanced to hang the hind legs of seve- 
ral frogs, by copper hooks, from the iron railing of the 
balcony of his window. As often as the wind, or any 
accidental cause, brought the muscles into contact with 
the iron bar, the legs were convulsively agitated. The 
astonishment of the experimenter can scarcely be con- 
ceived. In undertaking to account for an old fact, he 
had stumbled upon a most important discovery. The 
theory which he proposed was not correct, but the re- 
sults to which the observation have since led are as- 
tounding. The telegraph, the electrotype, and many 
metals discovered by galvanic means, may all be re- 
garded as its offspring. 

302. Explanation. — The convulsion 

Explain the \ . . 

above expert- produced in this case, is entirely analagous, 
in its course, to that described in the last 
paragraph. The two metals, the moist muscle, and 
the wind, to produce contact and so complete the cir- 
cuit, are all the conditions essential to the production 
of a current, and consequent contraction of the nerves. 



129 



PAET II. 



LAWS OF COMBINATION. 



CHAPTER L 

303. Number of elements. — The num- 
What is the b er f elements or simple substances at 

number of the 

elements? present known is sixty-two. Only thirty- 
five of these are of sufficient importance 
to be considered in this work. The rest are of rare 
occurrence, and are found in comparatively small 
quantity. 

304. Subdivision of the elements. 

How are the . 

elements sub- The elements may be divided into metals, 
and metalloids or non-metallic substances. 
They are thus divided in the table given on page 
131. Hydrogen and oxygen belong to the class of 
non-metallic substances, but are placed by themlseves, 
for reasons which will appear in the sequel. 

305. Atomic constitution. — All of the 

Of ichat are 

ihe elementary elementary substances, whether they be 
iuh *i an ^* ? solids, liquids, or gasos, are regarded as 
made up of minute atoms, as explained 
6* 



130 



ATOMIC WEIGHTS. 



in Chapter I. All of the atoms of the same substance 
are alike in every respect. 

306. Combination by atoms. — When 
How does ^ combination takes place between portions 

combination x r 

take place? of any two elementary substances, it may 
be regarded as consisting in the attrac- 
tion and juxtaposition of their individual molecules. 
Thus, when zinc tarnishes in the air, each of the 
atoms which form the surface of the zinc, takes to 
itself an atom of oxygen from the air, and the whole 
surface becomes covered with molecules of oxide 
of zinc. In the same manner, sulphuric acid is 
made up of compound molecules, each one of which 
consists qf an atom of sulphur, and three of oxygen. 

307. Atomic weights.— -Although the 

What is _, 

known of the atoms of all substances are too small to be 
TtomsV^ separately seen, chemists believe, not only 
that they have evidence of their existence, 
but that they know their relative weight. The rela- 
tive weight of the atoms of a few of the elementary 
substances, as compared with the hydrogen atom, 
which is the lightest of all, is given in the following 
table, as nearly as it can be given in whole numbers. 

308. It is to be borne in mind that the 
table which table does not undertake to tell the absolute 
vnderst ^dJ we ^g' lt °f t ' ie hydrogen atom, or of any 

other atom. This is not known. It only 
informs us that whatever may be the weight of the 
hydrogen atom, that of oxygen weighs eight times, 
that of sulphur, sixteen times, and that of carbon, six 
times as much : and so on of the other elements. 



ATOMIC WEIGHTS. 



131 



TABLE OF SOME OF THE MORE IMPORTANT ELEMENTS AND 
THEIR COMPOUNDS. 



METALLOIDS. 



Name. 
Hydrogen, 
Oxygen, . 



Symbol. Atomic weight. 

. H 1 

. . O 8 



Name. 
Nitrogen,. 
Chlorine, . 
Phosphorus, 
Sulphur, . 
Carbon, . 



METALLOIDS. 

Symbol Weight, 

. . . N 14 

... CI 35 

. P 32 

. S 16 

. C 6 



METALS. 



Name. 
Potassium, . 
Sodium, . , 
Calcium, . , 
Magnesium, . 
Barium, . . 



Symbol. Weight. 
. K 39 

. Na 23 

. Ca 20 

. Mg 12 

. Ba 68 



Metalloids with Oxygen form 
ACIDS. 

Nitric Acid, N0 5 

Chloric Acid, ..... C10 5 
Phosphoric Acid, . . . P0 5 
Sulphuric Acid, .... SO3 
Carbonic Acid, .... C0 2 



Metals with Oxygen form 
OXIDES or BASES. 

Potassa, KO 

Soda, NaO 

Baryta, BaO 

Calcia, CaO 

Magnesia, MgO 



Nitrate of Potassa, , 
Nitrate of Soda, 
Nitrate of Baryta, 
Nitrate of Calcia. . 
Nitrate of Magnesia, 



Acids with Bases form 
SALTS. 



KO,N0 5 
NaO,N0 6 
BaO,N0 5 
CaO,N0 5 

MgO,N0 5 



Sulphate of Potassa, KO,S0 3 
Sulphate of Soda, . NaO,SO, 
Sulphate of Baryta, BaO,S0 3 
Sulphate of Calcia, . CaO,S0 3 
Sulphate of Magnesia, MgO,S0 3 



Each of the other acids forms its class of 6alts. There are other 
classes of acids, to be hereafter mentioned, which contain no oxygen. 



What do metalloids form with oxygen 1 Give some examples. 
What do metals form with oxygen? Give some examples. 

What do acids form with bases ? Name all of the salts which may be formed 
from the acids and bases above mentioned. 



l32 laws of combination. 

309. Explanation of the symbols.— 

What do the _ _ .. A j , , 

sj/wi6oZs rfanrf The symbols may best be regarded by the 
cZi P l^ iVe student as standing for single particles of 
the several substances. Thus, N, 01, P, 
K, Na, Ca, indicate respectively single atoms of Nitro- 
gen, Chlorine, Phosphorus, Potassium, Sodium, and 
Calcium, and the numbers in the next column of the 
table indicate the relative weight of the atoms. In the 
case of compounds, the symbols also show their compo- 
sition. Thus, N0 5 stands for a single molecule of 
Nitric acid, and, besides, indicates, as represented in 
the figure, that every such molecule is a com-/m 
pound molecule consisting of one atom of nitro- Ww 
gen, and five atoms of oxygen. 

What does 310. Again, KO stands for a single 

KO indicate ? mo lecule of Potassa, and indicates that i&& 
it is a compound consisting of one atom of potas- 
sium and one of oxygen. Such a compound of two 
elements is called a binary compound. 

311. In the same manner KO.NO, stands 

What does 7 * 

KO, NOi in- for a single molecule of Nitrate of ....* 

Potassa, and indicates that every i M^ \ 
such molecule is a compound, made up of two ' -S ■ ' 
other compound molecules, one of nitric acid, and an- 
other of potassa. Such a compound, of two binary com- 
pounds, is called a ternary compound. The symbols 
may, indeed, be regarded as standing for larger quan- 
tities, in the same relative proportion ; but it is an as- 
sistance in understanding chemical phenomena, to re- 
gard them as has been suggested. 



atomic weights. 133 

312. Atomic weights of compounds. 

How are atom- . 

ie weights of The relative weight of tne atoms of 
C deurmin€d? simple substances is given in tr.3 table. 
With the help of these and the symbols, 
the relative weight of the molecules of compounds is 
easily calculated. Thus, the symbol of nitric acid, 
being NO, , we know that 54 must be the weight of 
the molecule of nitric acid. For the symbol informs 
us that it is made up of a single atom of nitrogen (14) 
and five atoms of oxygen, (40). The weight of 
a molecule of potassa is 47, its symbol (KO) in- 
forming us, that it is made up of one atom of potas- 
sium, (39),and one atom of oxygen, (8). 

313. Calculations of weights from 

Howareabso- 

lute weights symbols. — Prom the symbols of com- 
fr l o™%mbch? pounds, the relative weight of their com- 
ponents may be calculated. N0 5 , being 
the symbol of nitric acid, we know, as above 
shown, that the weight of its least particle is 54, and 
that this weight is made up of nitrogen, 14, and oxy- 
gen, 40. As a larger quantity is composed of precisely 
such particles, the relative weight of the constituents 
must be the same. Fifty-four pounds of nitric acid, 
therefore, contain 14 pounds of nitrogen, and 40 pounds 
of oxygen. In the same manner, from the symbol 
KO, with the help of the table of atomic weights, we 
ascertain that 47 pounds of potassa contain 39 pounds 
of potassium, and 8 pounds of oxj'gen. CaO,S0 3 , is 
the s} r mbol of Sulphate of Lime or Gypsum. Adding 
the atomic weight of its constituents, we have 68 as 
the sum. Sixty-eight pounds of sulphate of lime, there- 



134 LAWS OF COMBINATION. 

fore, conta.n 20 pounds of calcium, 16 pounds of sul- 
phur, and 32 pounds of oxygen. 

314. Definite proportions. — The 
Illustrate the composition of the same substance is al- 

law of definite x 

proportions. ways the same. When hydrogen and ox- 
ygen unite, in the proportion of one of the 
former to eight of the latter, they form water. (HO). If 
an excess of either element is employed, it remains un- 
combined. When they unite in a different proportion, 
as they do in another process, they form not a some- 
what modified or changed substance, but an entirely 
new and distinct one, viz., peroxide of hydrogen, 
(H0 2 ) whose composition is also uniformly the same. 
So nitrogen combines with oxygen, in each one of 
the proportions indicated by the symbols, NO, N0 2 , 
NO, 3 N0 4} N0 5 , in each case forming a new substance. 

What is the 315. MULTIPLE PROPORTIONS. As COm- 

lawofmuiti' bination always takes place by whole at- 

ple propor- J x # . J 

tions? Give oms, and never by fractions, it is evident 
examples. that w h enever lt occurs i n m0 re than one 

proportion, the others must be multiples of the first pro- 
portion or atomic weight. Thus the proportions, by 
weight, in which oxygen unites with nitrogen, are 8 r 
16, 24, 32, 40. In other than such exact proportions, 
combination never takes place. 

316. Chemical equivalents. — It has 

WJiat iza , , . 

chemical already been shown that the atomic 

GivefrfJ- weights express the portion in which sub- 
ample. stances combine with each other. It also 

expresses, as would be naturally inferred, the propor- 
tions in which they replace each other, whenever such 
replacement occurs. Thus, chlorine sometimes expels 



EQUIVALENTS. 135 

and replaces oxygen in chemical compounds. When- 
ever this takes place, 35 parts of the former, by weight, 
are required to replace 8 parts of oxygen. These 
numbers, therefore, express chemical equivalents of 
the two substances, and in general, a table of atomic 
weights, is also a table of chemical equivalents. So, 
when sulphuric acid expels nitric acid from any of its 
salts, it replaces it in the proportion of 40, to 54. The 
atom of sulphuric acid is the equivalent of that of ni- 
tric acid in another sense. It has precisely an equiva- 
lent effect in neutralizing the base with which this acid 
may be combined. 

317. The composition of a mixture, is 
potition°ex- sometimes expressed by equivalents. Gun- 
pressedby powder, for example, may be described 

equivalents? x x ■ * 

as containing one equivalent of sulphur, 
one of nitre, and three of carbon. This signifies 
that it is composed of 16 parts of Sulphur, 101 of ni- 
tre, and 18 of Carbon, as may be ascertained, by cal- 
culation, from* the table of atomic weights. 

318. Names of oxides. — It will be ob- 
oxides named? served from the table, that the oxide of 
Gwe exam- potassium is called potassa ; the oxide of 

sodium, soda, and so on, each oxide hav- 
ing a special name, derived from the name of the 
metal. The oxides of most of the other metals, not 
mentioned in the table, have no special names, but are 
called oxide of iron, oxide of lead, oxide of zinc, &c. 

319. Names of salts. — In naming the 
named? Give salts of the oxides last mentioned, the 
example*. term oxidej is omitted, for the sake of 



136 LAWS OF COMBINATION. 

brevity. Thus, we say, nitrate of iron, sulphate of 
iron, phosphate of iron, instead of nitrate of oxide of 
iron, sulphate of oxide of iron, &c. 

320. Formation of oxides. — Most 

How are ox- - 

ides formed? of the oxides of the table are imme- 
Give an exam- lately formed as soon as their respec- 
tive metals and oxygen come together. 
Thus, out of silvery potassium and transparent oxy- 
gen, white potassa is instantaneously produced. But, 
it is more commonly necessary to heat a metal with 
oxygen, to form its oxide. The oxides are also called 
bases. They are further considered in Part. III. 
Whatcom- 321. As oxygen forms oxides, with 

pounds do metals, so chlorine, bromine, iodine, flu- 

chlorine, io- 
dine, sulphur, orine and sulphur, form, respectively, chlo- 

c-,forn rides, bromides, iodides, fluorides, and sul- 

phides. The latter are also called sulphurets. 

322. Formation of acids. — Simple con- 

How are acids ., .. .. n 

- formed ? tact of a metalloid, and oxygen, is not gene- 

Givean ex- rally sufficient to produce an acid. Heat is 

ample e r r 

one among the additional means employed. 
Thus, carbon or charcoal, heated with oxygen, or in 
air which contains it, is immediately converted into car- 
bonic acid. Different acids are sometimes formed, by 
the combination of different proportions of oxygen, 
with the same substance. The names by which these 
are distinguished, are given, for reference, in the App. 
- v 323. Formation of salts. — Most salts 

How are salts _ - n . . . 

formed ? may be formed . by simply bringing the 

Give an exam- proper ac id an( i oxl( \ e tOgther. TllUS ? 

as soon as liquid sulphuric acid and white 



INFLUENCE OF HEAT. 137 

magnesia come together, they unite and form sulphate 
of magnesia or epsom salt. But the stimulus of heat 
is often required, particularly when the acid, as well 
as the oxide, is a solid substance. The affinity be- 
tween acids and bases, is in accordance with the gene- 
ral law, that chemical attraction between substances is 
strongest, in proportion as they are most unlike, or op- 
posed to each other, in their properties. 

324. Properties of acids and bases. 

What are the 

properties of The properties of these two classes of 
acids and ba- com p 0un d s are opposite, and when brought 
together, they neutralize each other. Thus, 
when acid and soda are brought together, the acid taste 
of the former and the alkaline taste of the latter both 
disappear. Acids change certain vegetable blues to 
red. Bases restore the color. The experiment may 
be made with an infusion of litmus* in water. A leaf 
of purple cabbage answers the same purpose. Acids 
color it red, while potash and the alkalies change 
the red to green. 

325. Effect of heat to produce com- 

What is the . 

effect of heat bination. — It is seen from the foregoing, 

IZnbinatiln? that heat is often essential to chemical 
combination. This is almost always the 
case where both substances are solid. Beside height- 
ening their chemical affinity, heat has the effect of 
bringing^he particles into closer and more general con- 
tact, and, within the range of affinity, by the melting 

* Litmus is a blue vegetable pigment much used by chemists, for the 
purpose mentioned in the text. 



138 LAWS OF COMBINATION. 

or fusion which it accomplishes. Sulphur and iron, for 
example, require the aid of heat to bring about their 
union. The sulphur melts, and then combines with 
the iron. 

326. Further heating, has often just the 

Mention an- 

other effect of contrary enect. It causes substances al- 
heat. ready combined, to separate from each other 

again. This is especially the case, when one of 
them is a gas. Thus, if oxide of silver or gold is 
heated, the oxygen passes off in the gaseous form and 
leaves the metal behind. 

327. Heat owes its decomposing effect, 

Wlty does heat ... , . .. \ & _ 

have this ef- m this and similar cases, to the tendency 
f ect ' which it imparts to certain substances, to 

assume the gaseous form. And as all bodies would, 
probably, be gaseous, at a sufficiently high tempera- 
ture, sufficient heat would probably decompose all 
chemical compounds. 

328. Effect of solution. — The solu- 
effect of solu- tion of one or both of two substances to be 
tionl combined, has, in a multitude of cases, 
the same effect, in promoting chemical combination, 
as that produced by heat. The reason is also the 

same. It brings them into more general and thorough 
contact. This is illustrated in the case of ordinary soda 
powders, the two constituents of which, will not act 
on each other, unless one, at least, is dissolved. 

329. Electrical relations of ele- 

What are the _,, . . 1 

electrical rela- ments. — The metals are sometimes spoken 

tions of the Q f ag e i ec t r o-positive and the metalloids as 

electro-negative, for reasons given in the 



ELECTRICAL RELATIONS. 139 

chapter on galvanism. Electricity also resolves salts 
into the bases and acids which compose them. The 
acid goes to the positive pole, and is, therefore, elec- 
tro-negative. The base goes to the negative pole, and 
is, therefore, electro-positive.* 

* The laws of combination, and other subjects which belong to 
chemical philosophy, are further considered in the chapter on Salts, 
in the introduction to Organic Chemistry, and in the Appendix. Ad- 
ditional remarks on the atomic theory adopted in the text, are also 
given in the Appendix. 







PAET III. 
INORGANIC CHEMISTRY". 



What is oxy- 
gen i 



CHAPTER I. 
METALLOIDS. 

OXYGEN. 

329. Description. — Oxygen is a trans- 
parent and colorless gas, a little heavier than 

Zcul)* '** ihe atrnos phere. It is by far the most 
abundant substance in nature. One-fourth 

of the air, one-ninth of the ocean, and, probably, half 

of the solid earth, is oxygen. 

How is oxygen 330 . PREPAR- 
prepared ) AT I0N. Gase- 

ous oxygen is expelled from 

many substances which 

contain it, by the simple 

agency of heat. Chlorate 

of potassa and black oxide 

of manganese are such 

substances. 

Give the com- 331. Mix equal quantities of these ma- 

pUte process, terials, and heat half a tea-spoonful of the 




142 METALLOIDS. 

dry mixture in a test-tube, connected, air-tight, with two 
clay pipes, as represented in the figure. The connec- 
tions are made by winding the pipe-stems with strips 
of wet paper, folded in such a manner that the stopper 
thus formed tapers slightly toward the end. The first 
portions of gas, which contain an admixture of the air of 
the tube, are allowed to bubble through the water and 
escape. The rest is made to rise into a half-pint vial, 
which it gradually fills, by displacing the water. The 
vial has been previously filled with water, then 
covered with a bit of glass, and inverted in the wa- 
ter. If it is desired to hang it on the side of the 
bowl, a hook is then introduced, made of strong, 
doubled wire, the two parts being kept about half 
an inch apart, and the vial is then hung, by its help, on 
the side of the bowl ; or this may be dispensed with, 
and the vial held by the hand in its proper place, while 
the gas is collected. When the process is completed, 
vial and hook, if the latter has been used, are to be low- 
ered into the bowl, the mouth being carefully kept 
below the surface ; the hook is then removed, the mouth 
covered with a bit of glass, and the vial then inverted 
upon a plate containing a little water, and so kept until 
it is wanted for an experiment. All other gases, that 
are not absorbed by water, may be collected in the 
same manner. 

Explain the 332 - Explanation.— Although black 

process. oxide of manganese may be employed as 

a source of oxygen, it does not yield this gas at the 
temperature employed in the above experiment. But, 



OXYGEN. 143 

for reasons not well understood, the admixture of this 
or any other infusible powder, facilitates the evolution 
of this gas from the chlorate. At a red heat, part of 
the double portion of oxygen which the black oxide 
contains is expelled in a gaseous form. 

332. A Simpler method. — The above 

Give a simpler in- 

method of pre- method, for preparing oxygen, is here 
paring oxygen give ^ because it illustrates the mode of 

collection of gases in large 
quantities, and makes its 
accumulation visible to the 
eye. The oxygen needed 
for the following experi- 
ments will be more con- 
veniently prepared by pla- 
cing the mouth of the test-tube, containing the proper 
materials, in a wide-mouthed vial, and heating, as be- 
fore. As the gas is evolved, it will expel the air, and 
soon fill the vial. 

333. Iron burned in oxygen. — Make 

How can iron 

be burned in a coil of very fine iron wire, by winding 
oxygen ^ e latter around a pencil ; fasten one end 

into the middle of a cork, by slitting the lat- 
ter, and attach a fine splinter to the other end. 
Light the splinter, and introduce it into a vial 
of oxygen. The wire itself will take fire, 
and burn with brilliaLt scintillations. In this 
and the following experiments, the cork is to 
be placed loosely over the mouth of the vial, to pre- 
vent its violent expulsion by the heated gas. 





144 METALLOIDS. 

334. Explanation. — In this experiment 

What takes . _ . ' 

/>to« in Me the oxygen in the vial unites with the 

went?***™' * ron °^ ^e w * re > an( ^ becomes solid, in 
the form of oxide of iron. The oxide 
fuses into a small globule on the end of the wire, and 
occasionally falls, and melts its way into the glass. 
This is apt to be the case, even when water is left in 
the bottom, so that a vial is likely to be destroyed by 
this experiment. The process is exactly the reverse of 
tliat which takes place when binoxide of manganese is 
heated, to produce oxygen. In the one case, oxygen 
was driven from the metal ; in the other, it is drawn 
to it, though not in the same proportion. 

Describe the ta- 335. TAPER REKINDLED IN OXYGEN. — 

per experiment Introduce a newly extinguished taper or 
shaving, with a little fire at the end, into a vial of 
oxygen. It will be immediately rekindled. This ex- 
periment may be many times repeated without a new 
supply of gas. 
„-•■■.» 336. Combustion is more vivid in 

Jixplain the 

last expeH- pure oxygen, than in air, because the latter 

is diluted with other gases which do not 

take part in the combustion. 

337. Combustion of phosphorus. 

Descrzop the 

experiment Place a piece of phosphorus, of the 
with phospho- gize of a pea? on a piece of chalk, 

slightly hollowed out for the pur- 
pose and connected with a cork by a fine 
wire. Ignite the phosphorus and introduce 
it immediately into a bottle of oxygen. It 







OXYGEN. 145 

will bum with the utmost brilliancy, producing a light 
which the eye can scarcely bear. 

338. The white fumes which fill the 

MVliat acid re- _ "^ . . , £ 

suits from this bottle in this experiment, are composed ot 
experiment? p ar ti c les of phosphoric acid, which are 
produced by the union of the phosphorus and oxy- 
gen. They collect on the sides of the vial, and soon 
dissolve in water, which they absorb from the air. 
The water will be found to possess a sour taste, and 
to redden blue litmus paper, which is a characteristic 
of acids. 

339. Combustion of charcoal. — At- 

Describe the 

experiment tach a small piece of charcoal to 

with charcoal? & fine ^^ ignite one end of ^ 

thoroughly, and introduce it into a vial of ox- 
ygen, having a cork at the other end, as 
before. It burns with brilliant sparks. A piece 
of charcoal bark is best adapted to this pur- 
pose. 

340. Carbonic acid is formed in the 

What is pro- . 

duced in this above experiment, from the union of 
expeT carbon with oxygen. It is a gaseous acid, 

and cannot be seen. Neither can it be detected by 
its taste. But a piece of moistened litmus paper, held 
for some time in the bottle, will be reddened by it, and 
proof of the presence of an acid may be thus obtained. 
When wood burns it also yields carbonic acid. 

341. Definition of combustion. — A\\ 

Define com- r ., , . r 

lustion. °* the above experiments are cases oi 

combustion, and combustion may be defi- 
ned as combination of any two substances, attended by 

7 




146 METALLOIDS. 

light and heat. Metals which will not burn in the 
aii, because it is diluted oxygen, burn brilliantly, as 
has been seen, in pure oxygen. 

342. Previous heat required. — In or- 

It Ay is heat 

required to der that most substances may burn, they 

% tion? m ^ must first be heated > t0 increase their affin- 
ity for oxygen. Take carbon, as an exam- 
ple. Before heating, its affinity for oxygen is not suf- 
ficient to bring about the requisite combustion. In this 
condition it may, therefore, lie for any length of time, 
in the air, or oxygen gas, without uniting with it. 
But heat stimulates the tendency to combination, and 
the bit of charcoal previously ignited, goes on burning 
until it is consumed. The first particles obtain the 
necessary stimulus of heat, from the previous igni- 
tion, the next from the burning of the first, and so on. 

343. Uncombined oxygen requisite.— 

What hind of rn • 

oxygen is re- Mere presence of oxygen is not sumciant 
quired for £ com bustion. It must be free, or un- 

combustion f ' 

combined oxygen. After burning char- 
choal in oxygen gas, the vial contains just as much 
oxygen as before, but being already combined, it has 
no affinity, or appetite, for more carbon, and there- 
fore will not produce a new combustion. 

344. Each particle in turn must be 
:ie iTnofheat- heated. — If the first particles that com- 
id, what takes bine, do not communicate sufficient heat 

dace f Why f 7 

to the next, then the combustion stops. 
This may be illustrated by lighting a tightly wound 
oil of paper, and holding the flame upward. It is 
loon extinguished, because the heat that is produced 



OXYGEN. 147 

by the combustion of one portion of the paper, is not 
communicated to the next, but passes off into the air. 
But if the taper be held with the flame downward, 
each particle in turn receives the stimulus of heat ne- 
cessary to combination, and the whole is consumed. 

345. Decay of leaves and wood. — 

What causes 

the decay of The decay of leaves and wood is a sort 
wood? f g j ow com bustion, but not sufficiently 

vigorous to produce light and heat. In this case, as in 
the ordinary combustion of wood or coal, the particles 
which have combined with oxygen pass off into the 
air, in an invisible form. 
• 346. Bleaching. — Bleaching may also 

How may 

bleaching be be regarded as a kind of slow combustion. 
regar e . Q n exposing cloth to sun and air, its color- 

ing matter is gradually burned up by the atmospheric 
oxygen. 

347. Oxygen a purveyor for plants. 
oxygen^ 1 ™ ^ h as been seen that both in combustion 
purveyor for an( j decay, the oxygen of the air combines 
with the particles of leaves, and wood, and 
coal, and passes off with them in an invisible form. It 
flies off with them into the air, and yields them again 
to living plants, to produce new leaves and flowers, and 
fruits. Indeed, they are entirely dependent, for their 
support, on what they thus obtain from the death and 
decay of their predecessors, through the agency of this 
ever active purveyor, the oxygen of the air. But for 
the fact that the particles of vegetable and animal mat- 
ter can thus be used again and again, the supplv would 



148 METALLOIDS. 

soon be exhausted, and vegetation cease upon the face 
of the earth. 

348. Ozone. — By passing an electrical 
How is ozone current, continually, through oxygen gas, 
for some time, it. becomes mysteriously 
changed in its proportions. In this changed condition 
it is called ozone. It is, as it were, intensified in its affin- 
ities by the current, so that like chlorine, it will attack 
silver, arid exhibit many other of the properties of the 
latter gas. The electricity of the air has similar effects 
on the oxygen which it contains, and, in consequence of 
its varying electrical condition, the proportion of ozone 
is, also, from time to time, extremely varied. There is 
reason to believe that this substance has important influ- 
ence upon health, and that either its deficiency or excess 
is injurious. In cholera seasons, it has been observed 
to be present in comparatively small quantity, while, 
during the prevalence of a species of influenza called 
' grippe," it is said to be more abundant. These obser- 
vations need confirmation, by further experiments, before 
the facts can be regarded as fully established. The pres- 
ence of ozone, is indicated by the discoloration, through 
the influence of a current of air, of a test paper, de- 
scribed in the section on chlorides. 

. . 349. Relations to life. — Oxysren is 

What relation , ^ 

to life does ox- as essential to life, as it is to combustion. 

ygen sustain^. rp he diluted oxygen of the ^ ig better 

adapted to breathing, than pure air, but that which con- 
tains much less than its due proportion, is no longer 
fitted to support life. Respiration consumes oxygen, so 
that the air of a close room is constantly being depri- 



CHLORINE. 149^ 

ved of this essential constituent without obtaining any 
new supply. As a consequence, it soon becomes unfit 
to breathe. The case is similar to that of a taper 
burned in a bottle. The oxygen of the air in the bot- 
tle is gradually consumed, and the flame grows grad- 
ually more and more dim till it goes out. So life grows 
fainter and fainter, in a close, unventilated room. 
What is said 350. Oxygen has been used, with great 
of oxygen as success, as a means of resuscitation, in cases 

a means of ' ' 

resuscitation? of suffocation and drowning, when similar 
use of air was without effect. In such cases, it is forced 
into the lungs through a tube, from a jar or bladder. 

CHLORINE. 

What is chlo- 351. Description. — Chlorine is a yel- 
*™f* . . lowish green gas, of peculiar odor, about 
found ? %\ times as heavy as the air. More than 

one half of common salt is chlorine. Salt mines and 
the ocean, therefore, contain it in immense quantities. 
352. Preparation. — Chlo- 

How is chlo- . r 

Hneprepar- rine is prepared from muriat- 

* d? ic acid, which is composed of ^ 

chlorine and hydrogen, by using some 

agent to retain the latter and liberate the 

former. Black oxide of manganese is* 

such a substance. 

Give the com- 353. The oxide is well covered with mu- 

plete proceeds. r j a ti c acid, and kept warm, as the evolution 

of the gas proceeds. This is best effected by a cup of 

hot water, as represented in the figure. Chlorine gas 

soon displaces the air in the second vial. It should be 

corked as soon as filled. 




150 



METALLOIDS. 



Explain the 354. It will be remembered that black 

process. oxide of manganese, is a substance con- 

taining a. large portion of oxygen, part of which 
is feebly held, and very willing to go. Its use in 
making chlorine depends on this fact. The loosely 
held oxygen, seizes upon the hydrogen of the muri- 
atic acid, remaining with it as water, and at the same 
time setting its chlorine at liberty. 

355. A simpler method. — Acids expel 

Describe an- . . 

other method chlorine from many bases which have 
of preparing prev i ous i y been made to absorb it. 

chlorine. r J 

Lime is one of these bases. Pour 
into a wide-mouthed, half-pint vial, a table 
spoonful of dilute sulphuric acid, and add 
rather more than the same bulk of chlo- 
ride of lime or bleaching powder. It is best 
to add it in small portions, covering the vial 
with a cork or bit of glass after each addition. 
The vial will soon be filled with faintly green chlorine 
gas. More of the materials will be required, if the 
chloride of lime is deteriorated by exposure to the air. 
as is often the case. The gas thus produced, may be 
used for most of the experiments which follow, with- 
out transferring it to another vessel. 

356. Chlorine heavier than 

What proof . . 

that chlorine air. — This is already imperfectly 
is heavier pr0 ved, in the first method of col- 

than airs r 1 

lecting chlorine, but the follow- 
ing proof is more satisfactory. The gas pro- 
duced in the last experiment, may be slowly 
poured from the vessel containing it, into 





CHLORINE. 



151 



What proof 
that chlorine 
dissolves in 
water / 



another wide-mouthed vial. The second vial, if 
the smaller of the two, may be thus filled without re- 
ceiving any acid from the first. In small quantities 
the gas cannot be seen to flow, but will actually pass 
from one vessel into the other. Its presence may be 
proved by the methods given in the following experi- 
ments. 

357. Chlorine dissolves in water. — 
Having filled a vial with chlorine, by the 
first of the methods above described, cork it, 
and open it under water, contained in a 

bowl. As the gas dissolves in the water, 
the latter will rise to take its place. When 
it has risen a little way, cork and shake 
the vial, and open it again below the 
surface. The water will then rise and 
dissolve still more of this gas. The so- 
lution is to be set aside for a subsequent experiment. 
Gas produced by the second method above described, 
may also be used in this experiment, if previously 
transferred to another vial. 

358. Action of chlorine on metals. 

Describe the . 

action of chlo- Chlorine gas combines with many metals, 
vine on metals. converting them int0 chlorides. Their ac- 
tion may be illustrated by sprinkling finely pulverized 
antimony into a bottle of chlorine. Each particle of 
metal ignites as it falls through the gas, and a minia- 
ture shower of fire is thus produced. The white smoke 
which is produced in this experiment, is composed of 
^rinute particles of chloride of antimony. 




152 METALLOIDS. 

™ A . A , 359. Nascent chlorine. — Nascent chlo- 

Wkat is the 

action of nas~ line, in its action on the metals, is the most 
cent chlorine^ powerful agent known< Even the noble 

metals yield to its power, and waste away in the liquid 
which contains it. The term nascent signifies being 
born, or in the act of formation. 

What is the 360 ' All gases are most energetic, in 

general fact their action at the first moment of their 

in relation to . 

nascent bo- separation from compounds which contain 
them, and while they may be regarded as 
still retaining the solid form themselves. The subse- 
quent expansion into the gaseous form, diminishes their 
energy. 

361. Nascent chlorine is best obtained 

How is nas- .. . . * . 

cent chlorine by mixing hydrochloric acid with half its 

best obtained? bu j k of strQng nitric add guch & mix _ 

ture is called aqua regia. The latter acid compels the 
former to yield a constant supply of its own chlorine in 
the nascent condition. It does this, by means of its oxy- 
gen, which seizes upon the hydrogen of the hydrochlo- 
rine acid, forming water, and sets its chlorine at liberty. 
The remnant of the nitric acid escapes, as in the case 
of its action on metals hereafter described. 

362. Chlorine decomposes water. — 

Does chlorine 

decompose wa- If chlorine water be exposed to the sun 
for some days, it loses its green color. 
The chlorine combines with the hy- 
drogen of the water, forming hydro- 
chloric acid, and sets its oxygen at 
liberty. If the experiment be made in 
a bottle, inverted in water, so that the 




CHLORINE. 153 

oxygen may collect, bubbles of this gas will be found 
above the liquid. This experiment proves the pow- 
erful affinity of chlorine for hydrogen. 

363. Bleaching by chlorine. — Intro- 

How is ca/ico . 

bleached by duce bits of calico into the solution 01 
chlorine I chlorine before obtained. Most colors will 
soon disappear. If the solution is weak, the bleaching 
effect will be better shown with infusion of litmus or 
red cabbage. Color may also be removed from cloth 
or paper by hanging the article to be bleached, pre- 
viously moistened with water, in a vial of gaseous 
chlorine. 

364. Chlorine water may be prepared 

How is chlo- 
rine water best in larger quantity, by leading the gas di- 

prepared? ^^ ^ water> The firgt of the twQ 

methods before described, will be found the most ad- 
vantageous. 
^ 7 . , 365. Oxygen the real bleaching 

Explain how m 

chlorine agent. — The real bleaching agent in this 

method of bleaching, is the same as that 
mentioned in paragraph 346. It is oxygen, always 
present during the process, as an element of the water 
which moistens the material. The chlorine simply 
acts to bring nascent oxygen into activity. It does 
this by depriving it of the hydrogen with which 
it is combined. The oxygen having thus lost its com- 
panion, looks about, as it were, for something else 
with which to combine. The coloring matter of the 
cloth being the first thing at hand, is destroyed by the 
extreme energy of its affinity. 
7* 



154 



METALLOIDS. 



Describe the 
inflaming of 
turpentine by 
chlorine. 



366. Action of nascent oxygen. — The 

Show the ad~ . 

vantage of superior force of an element in its nascent 
nascent oxy- condition is strikingly shewn in the above 

gen. & J 

experiment. A piece of calico hung 
in a bottle of oxygen gas would not lose its color. 
But the nascent oxygen which chlorine liberates, be- 
gins to destroy the coloring matter on the first instant 
of its liberation. 

367. Chlorine and turpentine. — Im- 
merse a rag wet with camphene or spirits 
of turpentine in a vial of chlorine 
gas. It is immediately inflamed, 

with the production of dense black smoke. 
Spirits of turpentine is composed of hydro- 
gen and carbon. The former combines so 
energetically with chlorine, as to produce 
flame in the above experiment, while the latter 
is separated in the form of black particles, which con- 
stitute the smoke. 

368. Use as a disinfectant. — As chlo- 

Jo chlorine a 

disinfectant ? rine destroys color, when used as a bleach- 

Why 2 • t 

y * mg agent, so it destroys noxious vapors in 

the air. Its minute atoms fly forth like birds of prey, 
seizing on the impurities of the atmosphere and de- 
vouring them. Chloride of lime is commonly substi- 
tuted for chlorine for this use. A little of this salt is 
placed in a saucer and moistened, when it gradually 
yields chlorine through the action of the carbonic acid 
of the air. Stronger acids evolve it abundantly. 




chlorine. 155 

369. Chlorine a destructive agent. 

What is said . . r 

of chlorine as Chlorine, as has been seen, is one 01 the 
a destructive mos t destructive of all substances. It not 

agent s 

only destroys colors and odors, but any 
kind of vegetable or animal matter long submitted to 
its action, wastes away and is destroyed. It does this 
partly by its own direct action, and partly by letting 
loose the atoms of nascent oxygen, as before described. 

370. In what sense destructive. — It 

In what sense 

is it destruct- is always to be borne in mind that the 
term destruction is used in chemistry in an 
entirely figurative sense. Thus, neither oxygen nor 
chlorine, strictly speaking, destroy. They only com- 
bine with the particles of the substances they seem to 
destroy, forming new, and often invisible compounds. 
Many of these will be hereafter mentioned. 
^ 371. Relations to animal life. — Chlo- 

Give the rela- . 

tions of chio- rme is a poisonous gas. No danger, how- 
U/e. t0 anlmal ever > is t0 be apprehended from the escape 
of small portions into the air during the 
preceding experiments. The diluted gas, however, is 
apt to produce irritation of the throat and consequent 
coughing. 

In what re- 372. RESEMBLANCE TO OXYGEN. In 

fhTorin^re- man Y respects chlorine is similar to oxy- 
semble oxy- gen, as has already been shown. It com- 
bines with almost all of the elements, and 
with many compounds. This combination is often 
attended with light and heat, and is therefore com- 
bustion. The metal antimony, for example, as has 



156 



METTALLOIDb. 



already been shown, will burn in chlorine gas even 
without kindling. 

Mention some 3 ^3. COMPOUNDS OF CHLORINE AND OXY- 

compound* of GEN# — Chlorine combines with five atoms 

chlorine and . 

oxygen. of oxygen to form chloric acid. This acid 

is of importance, principally, as a constituent of the 
cKlorate of potassa, analagous in its leading properties 
to nitrate of potassa. Hypoclorous acid, a constitu- 
ent of bleaching powders, is another compound of chlo- 
rine with oxygen. It is again mentioned in the section 
on Chlorides. 

IODINE. 



374. Description. — Iodine is commonly 

Wliat is io- 
dine? Where seen in the form of brilliant blue-black 

is it found. sca ] es? somewhat similar to plumbago in 

appearance. In odor it resembles chlorine. It is found 

in the water of the ocean, in sea-weeds, sponges, &c, 

but always in combination with sodium or some 

other metal. Minute traces of it are found to exist in 

the atmosphere, and thence are transferred to the bodies 

of animals. 

, . , 375. Preparation. — For the preparation 

Explain the 

manufacture ol iodine, a lye 

of iodine? 



made from the 
ashes of certain sea-weeds 
is heated with oil of vitriol 
and black oxide of manga- 
nese. The liberated oxy- Jjj^-r 
gen of the latter expels va- 





IODINE. 15? 

pors of iodine from the mixture. These being led into 
a receiver, crystallize in brilliant scales. A retort and 
receiver are commonly used in the process. The ashes 
of sea-weed employed for the purpose are called kelp, 
and are prepared in great quantities on the coast of 
Scotland. 

376. Violet vapors of iodine. 
vioZfvapors Introduce a few scales of iodine into 
of iodine pro- a test-tube or vial, and heat it for 

duced? 

a moment over the spirit lamp. The 
solid iodine is immediately converted into a 
beautiful violet vapor, which fills the vial. As 
the latter cools, the iodine becomes again solid, 
in the form of minute crystals. On warming 
these crystals the color re-appears. 

377. Coloring effect on starch. — 
Describe the jj eat a little iodine in a pipe 

effect produ- r * 

ced by iodine bowl, and as soon as vapors ap- 
p^ste^ pear, blow them against a sheet 

of paper covered with figures 
made with thin starch paste. The iodine vapor imme- 
diately colors them blue. The paste may be made in 
a test-tube, over a spirit lamp. 

378. Engravings copied by iodine. — 

How are en- . . 

graving* copi- A transient copy of an engraving, or other 
ed by iodine? printed matter, may be made, by exposing 
it to faint fumes of iodine, and then pressing it down 
upon paper moistened with vinegar, or dilute nitric 
acid. The vapors, adhere to the ink only, and are 
transferred by pressure ; producing, with the starch 
contained in ordinary letter paper, a blue impression. 




158 METTALLOIDS, 



BROMINE. 



379. Bromine is a dense reddish-brown 

What is said n -j it j ■ 

of bromine? fluid, exhaling at ordinary temperatures a 
deep orange-colored vapor. It is similar, in 
its chemical properties, to chlorine, but the latter is 
the stronger of the two and expels bromine from its 
compounds. Thus, if chlorine be passed into one end 
of a heated tube containing bromide of silver, the va- 
pors of bromine will be seen to pass out at the other 
end, and escape, while the chlorine remains, and takes 
possession of the metal. Bromine, like chlorine, is 
found in sea- water and in the water of mineral springs, 
combined with sodium or some other metal. The 
power of chlorine to expel it from its compounds, is 
made use of in manufacturing bromine. This sub- 
stance is used in photography, but is otherwise of little 
general interest. Although widely distributed, it ex- 
ists in nature in comparatively small quantities. Bro- 
mine vapors have the effect of imparting to starch a 
beautiful orange color. 

FLUORINE. 

What is said 3 8°- Fluorine is a yellowish-brown gas, 
of fluorine ? f s t r0 ng odor, somewhat similar to that of 
chlorine. It is one of the elements of the beautiful 
mineral Jluor spar. It is prepared from the fluoride of 
potassium, by means of the galvanic current. Its isola- 
tion has been attended with great difficulties, and the 



SULPHUR. 159 

gas is therefore imperfectly known. Its principal com- 
pounds are hydrofluoric acid and fluor spar, to be here- 
after described. * 

SULPHUR. 

381. Description. — Sulphur is a brittle 

What is ml- .. * •-- . _. _ 

phur? Where yellow solid, burning with a peculiar odor 
does it occur . ma( j e f am iliar in the ignition of common 
friction matches. With the metals it forms sulphides 
or sulphurets. In Sicily and certain other volcanic 
regions, it occurs in beautiful, yellow crystals. Gyp- 
sum, and iron pyrites or fools gold, represent the two 
principal classes of minerals that contain it. It also 
enters in small proportion into the composition of all 
animal and vegetable substances. It is the sulphur in 
eggs that blackens the silver spoon with which they are 
eaten. 

382. Preparation. — In preparing com- 

Describe the t t . •''■■* 

manufacture mercial sulphur, the impure material of 
cf supiur . volcanic regions is highly heated, and thus 
made to fly off as vapor, leaving its earthy impurities 
behind. The vapors are condensed as flowers of 
sulphur. The process by which a solid is thus vap- 
orized, and re-converted into a solid, is called sublima- 
tion. Native sulphur may also be partially purified by 
simple fusion. Its earthy impurities having settled, 
it is poured off into moulds and thus converted into 
roll brimstone. 

* Many compounds of chlorine, bromine, iodine and fluorine, with 
each other and with ox3~gen, are known to the chemist, but they are 
without interest to the general student 



16u mkttall01.ds. 

383. Sublimation of Sulphur. — 
SSO£' The sublimation of sulphur may be 
of sulphur be shown by heating a small bit of the 

shown? . 

substance m a test-tube. Flowers 
of sulphur will deposit in the upper portion of 
the tube. 

384. Combustion of Sulphur. — % 

What is said ^ - , , 

of the com- Melt some flowers oi sulphur upon 
bustionof th d £ wi W ound with cotton 

salphur i 

thread, and hang them after ignition in a 
vial of oxygen gas. The oxygen gas com- 
bines with the sulphur, forming a new com- 
pound gas, called sulphurous acid. A bril- 
liant blue flame accompanies the combina- 
tion. It thus appears that acids may be gase- 
ous as well as liquid. The acidity may be 
proved, as usual, by blue litmus paper. 

385. Bleaching by Sulphur.- — Intro- 

Describe the . 

process of duce a red rose or other flower into a vial 
firJf^i- fiHed with sulphurous acid. It will soon 
phur ? lose its color. Wash it with dilute sulphu- 

ric acid and the color re-appears This experiment 
may also be made in a bottle in which sulphur has 
been burned in common air. 

386. Explanation. — Sulphurous acid 

Why r'oes suU . 

phurous acid forms a white compound with the red color- 
bleach? j n g ma ^ er f the rose. It may seem incom- 

prehensible that a colorless gas and red coloring 
matter should unite to form white, and it would be 
so, were the case one of mere mixture. But it is an 




SULPHUR. 161 

instance of chemical combination, in which, as is often 
the case, the properties of the constituents entirely dis- 
appear. When sulphuric acid is afterward used, the co- 
lor re-appears, because the stronger acid has expelled 
the weaker and has itself no inclination to form with 
the coloring matter a similar combination. 

387. Straw bleaching. — The bleach- 

Describe the • r j • i re . j r 

process of m S °* straw goods is always effected by 
straw bleach- sulphurous acid. They are first moistened, 
and then exposed to the fumes of burning 
sulphur. An inverted barrel is often made to serve 
the purpose of a bleaching chamber. Articles thus 
bleached by sulphurous acid, after a time, regain their 
color. This is not the case in chlorine bleaching, be- 
cause the coloring matter is not merely changed, but 
destroyed. This agent is not applicable to straw, on 
account of a faint brown tinge which it imparts to the 
material. 

388. Copying medal- 

3S? * Li °^ - Sul P hur melts > 

medallions by readily, by application of 

sulphur. i-i 

heat. At a higher temper- 
ature it thickens again. Still further 
heating makes it again fluid. In 
this second period of fluidity, it has the remarkable 
property of assuming a waxy consistence on being 
poured into water. In this condition it is used for 
copying seals, coins, and medals. The copy acquires, 
in a few hours, the original hardness of sulphur. The 
plastic material may be obtained in the form of elastic 





162 MKTTALLOID5, 

strings, by pouring molten sulphur from a test-tube 

into cold water. 

TT 389. Sulphur crystals. — Sulphur may 

How may cry s~ r j 

talsof sul- be obtained in a crystalline form, by melt- 
fa w/° in ? & * n a pip e bowl, at a gentle heat, and 

then allowing it to cool. A crust 
soon forms on the top, which is broken, and a 
portion of the liquid sulphur below poured out. 
On breaking the pipe, it is found filled with crystals, 
shooting across the interior from the encrusted walls. 



SULPHURIC ACID. 

Describe sul- 390. Description. — Sulphuric acid is a 
pkuHc Mid, colorless, oily fluid, of intensely acid taste, 
known in commerce as oil of vitriol It is composed 
of sulphur and oxygen, in the proportion of one atom 
of the former to three of the latter. It also contains 
water, with which it is chemically combined. As 
it is among the most important of all chemical 
products, the process of its manufacture will be given 
with some detail. 

391. Preparation. — Sulphuric acid may 

How may sul- - , .. - . . 

phuric acid be be made directly from its elements, by lg- 
prepare . nit in g a mixture of air and vapor of sul- 
phur with a red-hot iron. In quantity, it is always 
made from sulphurous acid, by imparting to the latter 
additional oxygen. Take a bottle in which sulphui 
has been burned, and which, therefore, contains sulphur- 
ous acid, and hold in it, for a short time, a rod or stick 




sulphuric; acid. 103 

moistened with nitric acid. The gaseous sulphurous 
acid obtains oxygen from the nitric acid, which is rich 
in this element, and very liberal of it, and thereby be- 
comes sulphuric acid. A little water, previously placed 
in the bottom of the vial, absorbs the acid 
thus formed. To acidify the water to any 
considerable extent, it will be necessary to 
burn sulphur, and introduce the moistened rod 
repeatedly. That the acid is not the sulphu- 
rous or the nitric acid, employed in the pro- 
cess, may be proved by using it to make hy- 
drogen gas. 

392. Remark. — The red fumes which 

What canaes 

the red fumes ml the vial in the last experiment, consist 
in the above of the c h an ged nitric acid, (nitric oxide,) 

experiment ? ° 7 v 7 J 

which has just given up part of its oxy- 
gen, and is now resuming part of it from the air. It 
thereby becomes a third substance, of a red color, to 
be again mentioned in the section on nitric acid. 

393. Manufacture of oil of vitriol. 

Explain how ___ . ' v "- _ ^ • 

sulphuric acid — The method of the production of oil 
]u™j nv f ac ~ of vitriol on a large scale, is essentially the 
same as that above given. Fumes of 
burning sulphur and vapor of nitric acid, with air and 
steam, are introduced into a leaden chamber, when the 
process proceeds, as before described. 

394. Comparatively little nitric acid is 

Why is but . r .... ,. 

little nitric needed in the process, for it is found that 

acid required? whi j e ^ yield§ OX y geil t0 the sulphurous 

fumes, the changed acid greedily seizes oxygen from 
the air of the chamber, and imparts it again, to keep up 



104 



METALLOIDS. 




the process. The air is, therefore, the real oxidizer, 
while the changed nitric acid only acts to transfer it 
to the sulphurous fumes. 

Describe the 395. DESCRIPTION OF ACID CHAMBERS. 

acid chambers. rp he fi gllre represents one form of the 
leaden chambers 
employed in the 
above manufac- 
ture. Connect- 
ed with them 
are a steam boiler and two furnaces, in one of which 
sulphur is burned, and converted into sulphurous acid. 
Over the sulphur is another vessel, containing the 
materials for making nitric acid, the formation of which 
commences as soon as the sulphur flame has imparted 
the requisite heat. The vapors thus produced, are 
mingled with air and steam in the leaden chamber. 
How they act together to produce sulphuric acid, has 
been already explained. The space is divided by a 
partition, in order that all the materials may be more 
thoroughly mixed, as they pass through the narrow 
opening below it. The acid, as it forms, dissolves in 
water which covers the bottom of the chamber, and is 
thus collected. Lead is used as a lining for the cham- 
bers, because the acid woul-d destroy almost any othei 
material that might be employed. 

396. The dilute acid obtained from the 

flow is the . n 

chamber acid chambers, is concentrated first in leaden 

lte vessels, and afterward, when it has become 

strong enough to corrode the lead, in retorts of platinum. 

The metal platinum being of about half the value of 



SULPHURIC ACID. 165 

gold, the vessels in which the evaporation is carried 
on are extremely expensive. Some manufactories de- 
liver tens of thousands of pounds of sulphuric acid per 
day. 

397. Comparative strength of sul- 

How is the ' . . . ; 

strength of PHURIC ACID. ■ bulphliriC acid IS the 

sulphuric acid strong r es t f a n acids. This may be shown 

shown ? • o J 

by bringing it to a direct trial of strength 
with other strong acids. If poured, for example, on 
nitrate of potassa, which is, as its name implies, a com- 
pound of nitric acid and potassa, it takes sole possession 
of the base and expels the nitric acid in the form of 
vapor. It expels muriatic acid from its compounds in 
the same manner. This is the method by which nitric 
and muriatic acids are always obtained. Whatever 
they can accomplish when free, may therefore be 
traced back to the power of sulphuric acid which gave 
them their liberty. The latter is the king among the 
acids, who accomplishes indirectly, what he cannot ef- 
fect in person. The solution of the noble metals by 
aqua regia is one among these indirect results. 

398. Sulphuric acid is volatile at high 

Is it strongest . 

at high tempe- temperatures. Phosphoric and other non- 
volatile acids, are, therefore, under certain 
circumstances, superior to it. This is illustrated in cer- 
tain crucible operations, where compounds containing 
sulphuric acid are heated with such acids. The sul- 
phuric acid is then easily dispossessed, and compelled 
to take refuge in flight. 

What is the 399. ACTION OF SULPHURIC ACID ON 

action of sul- METALS# — Sulphuric acid attacks all metals 

phunc acid * 

on metals. with the exception of platinum and gold. 



166 METALLOIDS. 

Even the dilute acid acts on all the metals hereafter 
named, as far as manganese. 

400. The action of the dilute acid may 

Illustrate the 

action of the be illustrated, by placing a few bits of zinc 
in a tumbler, with a little water, and ad- 
ding a small portion of oil of vitriol. The metal dis- 
solves with the evolution of hydrogen gas. The rea- 
son of the evolution of this gas is given in the sec- 
tion on Hydrogen. 

401. The action of the strong acid may 

Illustrate the . 

action of the be illustrated, by heating a little copper, 

strong acid. ^ q[{ q{ ^^ ^ ft y^j^ f The 

metal dissolves with the evolution of sulphurous acid 
fumes. The reason of the appearance of sulphurous 
acid will be given in the next section. 

402. Affinity for water. — The affin- 
^nitfofmU il Y of sulphuric acid for water is so strong 
phurtc acid that it lays hold on every particle of the 

for water /..._. r _ , 

invisible aqueous vapor of the atmosphere. 
It finds it in what seems the driest air ; and every par- 
ticle which it catches it retains. It grows in bulk 
by what it thus drinks, as will be seen if a little oil of 
vitriol is left exposed to the air, for a few days, in an 
ppen vessel. It is sometimes necessary, in chemical 
operations, to free gases from all the aqueous vapor 
which is mixed with them. This is done completely 
by causing them to bubble through oil of vitriol, and 
again collecting them. 

403. Heat by Dilution. — When sul- 

Vihat talis . . 

place whensul- phuric acid and water are mixed, conden- 
a\WtedV ld U sat * on ta kes place, accompanied by eleva- 
tion of temperature. Fifty cubic inches of 



SULPHUROUS ACID. 167 

ml ptkVtAc acid and fifty cubic inches of water, when 
mixed, do not fill a vessel of the capacity of one hun- 
dred cubic inches, but fall about three inches short. 
Condensation has therefore taken place to the amount 
of three inches. Hfeat is, as it were, pressed out in 
such cases, as explained in the early part of this work. 
404. Wood charred by sulphuric 

Why does sul- 
phuric acid acid. — Wood dipped in oil of vitriol is 

soon charred. Wood is composed of car- 
bon, hydrogen and oxygen. The last two togethei 
form water. The affinity of sulphuric acid for water has 
been mentioned above. The acid and the wood being 
:n contact, it would seem that the hydrogen and the 
oxygen of the latter agree to combine and satisfy this 
demand. The carbon being at the same time isolated, 
appears in its natural black color. Sulphuric acid ex- 
erts a similar action on other vegetable substances. 

405. Important uses. — Sulphuric acid 
of sui- is largely employed for dissolving indigo, 

for use in dyeing and calico printing ; also, 
for converting common salt into sulphate of soda, as a 
preparatory step to the manufacture of carbonate of 
soda. It is also essential in the manufacture of super- 
phosphate of lime, an article now extensively used 
iii agriculture. Nitric and muriatic acids are pro- 
duced through its agency from nitre and common 
salt. 

SULPHUROUS ACID. 

What is sid- 406. Description. — Sulphurous acid is 

phurous add? a g aS; having the smell of a burning match. 

8 



168 



METALLOIDS. 



<«&= 



It is composed of sulphur and oxygen, in the proportion 
of one atom of the former to two of the latter. The ter- 
mination " ous" indicates, as in other cases, a smaller 
proportion of oxygen than is contained in some other 
acid composed of the same elements. 
TT . , 407. Preparation. — It has already been 

How is sue- J 

phurous acid shown that this acid may be prepared by 
P re P™ burning sulphur in oxygen. Another, and 

better method is to heat oil of vitriol with bits of cop- 
per. The oil of vitriol is thus 
deprived of part of its oxygen, 
and converted into sulphurous 
acid. The process may be con- 
ducted in a test-tube. By lead- 
ing the gas through a smaller 
tube into a vial partly filled with 
water, a solution of sulphurous 
acid may be obtained, possessed of the same bleaching 
and other properties as the gas itself. When the evolu- 
tion of the gas commences, the heat of the lamp is no 
longer required. 

408. Explanation. — Copper has a very 
strong affinity for oxygen, and takes it 

from the oil of vitriol, which possesses it in large pro- 
portion. The oil of vitriol, thus deprived of part of 
its oxygen, is converted into sulphurous acid gas. 

409. Use in preserving wines. — Sul- 

Why is sul- . . ... 

phurous acid phurous acid, in small quantities, is some- 
sometimes ad- ti s a( jd e( i to wine to prevent its sour- 

aea to wines f r 

ing. This change is owing to the absorp- 
tion of oxygen from the air. Sulphurous acid is a 




Explain the 
process. 



NITROGEN. 169 

substance possessed of an excessive appetite or affinity 
for oxygen. A small portion of it in a wine cask will 
seize on what little oxygen finds admission, and so 
prevent the deterioration of the wine. It destroys it- 
self in this act of protection, and is converted into sul- 
puric acid. 
rr 7 410. Use in sugar manufacturing. — 

How is sul- 
phurous acid The oxygen of the air so modifies the 

employed in .. ~ . ,. M . _ 

manufacture juice of the sugar-cane, that it cannot be 
ing sugar ? made to yield its due proportion of sugar. 
Sulphurous acid, by appropriating the oxygen to itself, 
prevents this effect, and is said to double the product. 
It is generally used in the form of its lime compound, 
called sulphite of lime. The objection to its use con- 
sists in the slight sulphurous taste which it imparts to 
the sugar. But this is said to be removed by clarifi- 
cation, at a loss of ten per cent., leaving still a large 
gain from the employment of the process. The bleach- 
ing effects of sulphurous acid have already been illus- 
trated. 



NITROGEN. 
411. Description. — Nitrogen isatrans- 

Wliat is ni- 

trogen ? parent gas, without taste or odor. It forms 

TJund? S lt a ^out four-fifths of the air we breathe. It 
occurs also in combination with other ele- 
ments in a solid form. One-fifth of the weight of the 
dried flesh of animals is nitrogen. It also enters into 
the composition of nitre and other salts. 



8 




170 METALLOIDS. 

Howisnitro- 412. Preparation. — Nitrogen is pre- 
(jen prepared? p are d from ordinary air by removing its 
oxygen. For this purpose a small portion of phospho- 
rus is floated on a slice of cork upon water, and then 
kindled, and a vial inverted over it. 
As it burns it abstracts the oxygen ; 
the water rises to take its place, and 
what is left of the air is nitrogen. 
The cork should be a little hol- 
lowed out, and chalk scraped into 
the cavity. Water must be poured into the saucer as 
the first portion rises into the bottle. The bottle is 
then cooled, either by water or long standing, and 
corked while yet inverted It is then shaken, to wash 
the gas. A piece of phosphorus, of the size of a large 
pea, is sufficient for the preparation of half a pint of 
gas. 

Explain the 413. Explanation.— The burning phos- 

proeess. phorus selects all of the oxygen atoms in 

the air, and, by combining with them, converts them 
into solid particles of a certain oxide of phosphorus 
called phosphoric acid. These particles at first ap- 
pear as a white smoke, and are afterward dissolved in 
the water. 

414. Nitrogen extinguishes flame. — If 

Docs nitrogen . 

extinguish a burning taper be lowered into the bottle ot 
1 un l]h nitrogen, as above prepared, it will be im- 

mediately extinguished. Flame is the brightness which 
accompanies active chemical combination, but here is 
nothing to combine. Nitrogen is a sloth among the 
elements, possessing no degree of chemical activity. 



the atmosphere. 171 

415. Principal office of nitrogen. — 
^ci^l% The Principal office of the nitrogen of the 
ficeofnitro- air is to dilute its oxygen. The latter, if 

gen ? 

pure, would soon consume our bodies as 
it hastens the combustion of a taper or other combus- 
tible. 

416. The atmosphere. — The air we 

What is the 

composition breathe, and which, to the depth of fifty 
°* miles or more, forms the crystal shell 01 

envelope of the globe we inhabit, is a mixture of nitro- 
gen and oxygen gases with aqueous vapor. It also 
contains small and varying proportions of carbonic acid 
and ammonia. 

. . 417. Proof that air is a mixture. — 

How is it 

proved to be a That it is a mixture, and not a chemical 
compound, is sufficiently evident from the 
fact that it possesses no new and peculiar properties 
different from those of its constituents. It is further 
proved to be a mixture, from the fact that heat, which 
is the usual attendant on chemical combination, is never 
occasioned when air is artificially produced by the ad- 
mixture of its constituents. 

What purpose 418. Use OF CARBONIC ACID AND AMMONIA 

is served by IN THE AIR — Carbonic acid and ammonia, 

its carbonic 

acid and am- although present in the air in extremely 
small quantity, subserve the most impor- 
tant purposes in administering to the growth of plants. 
They constitute the gaseous food of all forms of vege- 
table life, as will be more fully explained in succeeding 
chapters of this work. 



172 



METALLOIDS. 




remaining |ths is nearly all nitro- 



419. Analysis of the air. — The me- 

fnptrHon of t,lod b Y which the relative amount of ox- 
vitroiren deter- ygen and nitrogen in the air is determined 

mined i _ . 

has been already given. On burning phos- 
phorus under a glass jar, as there described, the water 
is found to rise and fill a 
little more than one-fifth of 
the vessel, thereby indica- 
ting that one-fifth of the 
air which it contained was ^ 
oxygen gas. The 
gen. In accurate experiments, a graduated tube is 
employed, instead of a jar or tumbler. It is not es- 
sential that the phosphorus should be ignited.. With- 
out ignition, it will gradually combine with all the 
oxygen, and remove it from the air contained in the 
tube. 

420. In order to determine the amount 
of aqueous vapor and carbonic acid in the 
atmosphere, a gallon or other measured 
quantity of air is drawn through tubes 
containing materials to absorb these sub- 
stances. This quantity is known by the increased 
weight of the tubes after the experiment is completed. 

421. The apparatus described. — The 

Describe the 
apparatus 



How is the 
amount of car- 
bonic acid wa- 
ter and ammo- 
nia deter- 
mined ? 



used in this 
analysis. 



apparatus used in the experiment is repre- 
sented in the last figure. It consists of a 
bottle or small cask, filled with water and 
provided with a cock below. The cock is turned, and 
as the water flows out, air -flows in through the tube to 
take its place. The quantity of air that has passed 



NITRIC ACID. 173 

through the tubes is known by the quantity of water 
that has flowed out from the cask. The materials em- 
ployed in the tubes are pumice stone drenched with oil 
of vitriol, in the first, to absorb the water ; and caus- 
tic potassa, in the second, to retain the carbonic acid. 
The method for determining the amount of ammonia 
in the atmosphere is essentially the same, muriatic acid 
being used as the absorbant. 

422. Proportional composition of 

What are the . 

proportions of the air. — 1 he proportions of the four 
the deferent constituents of the air above mentioned, 

constituents of ' 

the atmo- as obtained by the method just described, 

* p ( are about 21 per cent, of oxygen, 79 of 

nitrogen, 25V oth of carbonic acid, and T o,oV 0,00 oth of 
ammonia. The proportion of aqueous vapor is ex- 
tremely variable. That of carbonic acid and ammo- 
nia is also variable to a considerable extent. 

NITRIC ACID. 

What is nitric 423 - Description.— Nitric acid is a thin. 
*cid? colorless and intensely acid fluid. It cor- 

rodes metals instantaneously, with the evolution of deep 
red vapor. It is composed of nitrogen and oxygen, in 
the proportion of one atom of the former to five of the 
latter. It contains, in addition, water, with which it 
is chemically combined. It is possible to make it an- 
hydrous, or free from water, but such an acid is never 
used. 

Bow is nitric 424. Preparation. — Nitric acid exists 
acidprepared? [ n a dormant state in ordinary saltpetre. 




174 METALLOIDS. 

Its affinities being entirely satisfied by the potassa with 
which it is combined in that substance, it lies there per- 
fectly inactive. Sulphuric acid being stronger, has the 
power of taking its base, 
and expelling the acid in 
the form of vapor. In or- 
der to collect and condense 
the acid fumes, the mixture 
may be made in a test-tube, 
the mouth of which opens 
into a vial or flask. It is necessary to keep the vial 
covered with porous paper or cloth, and to moisten it 
frequently in order to maintain its coolness. Wher e 
larger quantities are prepared, a retort and well-cooled 
receiver are employed, as represented in the Appendix. 
425. Oxidation of metals. — If a little 

What effect m . 

has nitric add nitric acid is poured upon a copper coin, 
placed in a capsule or saucer, the coin will 
immediately begin to dissolve. It is not, strictly 
speaking, the metal which dissolves. One portion 
of the acid first converts the metal into oxide, by giving 
it part of its own oxygen. It thereby destroys itself, 
while another portion of undecomposed acid dissolves 
the oxide which is formed. One portion, in reality, 
sacrifices itself to satisfy the appetite of the other. Most 
other metals are similarly acted on by nitric acid. 
What is nitric 426 - Nitric oxide. *— The vapors which 
oxide? are gj ven ff i n the last experiment are 

* It will be observed that the term oxide is sometimes applied to 
compounds of the metalloids with oxygen. (See chap, iii, Inorg. 
Chein.) 



NITRIC ACID. 



175 



Describe ano- 
ther method of 
producing the 
red fumes. 



nitric oxide, changed by the air into which they rise. 
The nitric oxide is, so to speak, the fragment of nitric 
acid, which is left after three atoms of its oxygen are 
abstracted. Rising into the air, it combines with oxy- 
gen enough partly to supply the place of that it has 
just lost, and is thus converted into red fumes of per- 
oxide of nitrogen containing four atoms of oxygen. 
This compound is also called hyponitric acid. Still 
another compound of nitrogen with oxygen is de- 
scribed in the section on nitrates. 

427. Repeat the experiment of the last 
paragraph, placing the coin and acid in a 
small vial or test-tube, instead of a saucer, 
and collect the nitric 
shown in the figure. The collec- 
tion should not be commenced 
until a colorless gas is produced. 
It will be best to fill the vial 
to only two-thirds of its capa- 
city. Then lift it from the 
bowl, and let the remaining water run out. The air 
will immediately rush in and change the colorless ni- 
tric oxide to red vapors of the peroxide of nitrogen. 

How does ni- 428. OXIDATION WITHOUT SOLUTION. 

Nitric acid oxidizes tin and antimony but 
does not dissolve them. The experiment 
will be best made with tin-foil. After the action of 
the acid, it will be found converted into a white pow- 
der. Gold and platinum are neither dissolved nor ox- 
idized by nitric acid. 



oxide produced, as 




trie acid act 
on tin ? 



176 






METALLOIDS. 



429. Combustion by nitric acid. — As 

How may com ■ . . . , 

bustion be nitric acid contains much oxygen, combus- 

M? e <?id* n%m ^ on ^Y * ts means would seem to be a very- 
probable result. To 
prove that it has this effect, boil 
strong nitric acid in a test-tube, 
the mouth of which is filled with 
nair. As the vapors pass through 
they will cause it to smoke, and, 
if the acid is sufficiently strong, 
produce ignition. > 

430. Combustion of 

Describe t/ie 

experiment Phosphorus is readily 
wiihphospho- ignited by throwing it 

ruse o J o 

upon nitric acid. If 
the acid is not very strong, it must be previously 
heated. Particles of phosphorus scarcely larger than 
mustard seed should be used in this experiment. 




PHOSPHORUS.—- 




PHOSPHORUS. 
431. Description. — Phosphorus is a 
phorus? wax-like, and nearly colorless solid, read- 

er* does it {{ ignited by heat Qr f r i ct ion* It forms 

occur/ jo j 

part of the mineral apatite, which is a 
phosphate of lime. Bones also contain it in large pro- 
portion. It is never found uncombined. 

Howisitpre- ^32. PREPARATION. Phosphorus is 

pared? made from bones. These are composed, 

* When phosphorus is cut, it should always be under water, and 
every particle not used should be immediately returned to a bottle 
containing water. 




* PHOSPHORUS. 177 

principally, of gelatine and phosphate of lime. The 
individual constituents are gelatine, lime, oxygen and 
phosphorus. To obtain the phosphorus, all the rest 
are to be first removed. Fire removes the gelatine, 
oil of vitriol the lime, and charcoal the oxygen. 
Give the coin- 433. The bones having been previously 
picte process, burned, the ground ash is mixed with di- 
lute sulphuric acid and water, and, after several hours, 
filtered. Sulphuric acid unites with the lime, forming 
an insoluble sulphate, and at the same time sets the 
phosphoric acid at liberty. The solution containing 
phosphoric acid is then mixed with 
charcoal, and heated in an earthen^ 
or iron retort. The carbon takes the 
oxygen, and passes out of the retort with it, 
as gaseous carbonic oxide. The phosphorus which is 
left, being vaporized by the heat, is also expelled, but 
is reconverted into solid phosphorus by the cold water 
into which it passes. The figure will give some idea 
of the arrangement. The neck of the earthen retort 
passes into a copper tube, which leads into water. The 
gas produced by the process bubbles through the water 
and escapes, while the phosphorus is hardened by it 
and remains. The mass thus obtained is melted under 
water and run into moulds. 

434. Phosphorescence. — This term is 
pko™'cscence°?' applied to the luminous appearance of sea- 
water when agitated, and to other faint 
light unaccompanied by perceptible heat. It is ob- 
served when an ordinary friction match is rubbed upon 

the hand in the dark. The light is owing to a slow 
8* 



178 METALLOIDS. 

combustion of phosphorous, which takes place without 
kindling. The product of the combustion, is a white 
powder, caded phosphorous acid, which soon becomes 
liquid, by absorbing moisture from the air. ~S^ 

435. A harmless fire. — By agitating 

How may a 

harmless fire phosphorus with ether, a small portion of 
epio ace ^ e f ormer substance is dissolved. This 
solution, if rubbed upon the face and hands, makes 
them luminous, in the dark. This is another case of 
phosphorescence. A piece of phosphorous of the 
size of a pea is amply sufficient for the experiment. 

436. Combustion under water. — Phos- 

How may 

phosphorus be phorus may be burned under water by the 
water? UndeT kelp of substances rich in oxygen. Chlo- 
rate of potassa is such a substance. Place 
a few scales of this salt, and a bit of phospho- 
rous of the size of a pea, at the bottom of a 
wine glass previously filled with water. Par- 
tially fill the bowl of a pipe with oil of vitriol, 
and drop it in small portions on the mixture, 
bringing the pipe stem, each time, close to the bottom 
of the glass. As soon as the stronger acid is applied, 
chloric acid, containing much oxygen, is liberated and 
decomposed, and the phosphorus inflamed. A similar 
combustion of phosphorus, by means of nitric acid 
has already been described. 

437. Friction matches.— Ordinary 

vvhat is said 

of friction phosphorus is too inflammable to be em- 
matches i ployed in the manufacture of friction match- 

es. By heating it under carbonic acid for a long time, it 
becomes changed in color, and also less fusible and in- 




ARSENIC. 179 

flammable. In this form of red phosphorus, it is used 
in the manufacture of friction matches. 



ARSENIC. 
TT7 ^ 438. Description. — Arsenic is a grey 

Why is arsen- . 1 **•■«• 

ic introduced substance, oi metallic lustre, and for this 
metaUoidsf reason commonly classed among the met- 
als. On the other hand, in view of the 
compounds which it forms, and especially in view of 
the fact that its oxygen compounds are acids, and not 
oxides, it is more properly classed among the metal- 
loids. Its analogies to phosphorus are most striking, 
and it is for this reason here introduced, in immediate 
connection with that element. 

In what re- 439. ANALOGIES TO PHOSPHORUS. Ar- 

spectsdophos- sen [ c unites with oxygen in the same pro- 

phorus and _ J <-* x 

arsenic resem- portions as phosphorus, forming similar 

hie each other ? • ■, r^t r \. -it 

acids. 1 nese m turn form salts resembling 
each other most perfectly in external appearance and 
in crystalline form. It also combines with three atoms 
of hydrogen to form arseniuretted hydrogen, a gas 
analogous to phosphuretted hydrogen, to be hereafter 
described. Of the two principal oxygen compounds of 
phosphorus, the higher or phosphoric acid is the more 
important, and was therefore more particularly consid- 
ered. On the other hand, the lower or arsenious acid is 
the more important of the acids of arsenic. 
How is arsenic 440. Preparation.— Metallic arsenic is 
prepared ? found native. It may also be prepared 




180 METALLOIDS. 

from arsenious acid, by heating with a 
large proportion of carbon, as in the 
case of phosphorus, before described. 
Beside mixing with carbon, it is best, 
also, to cover with the same material, 
and heat from above, downwards. The metal passes 
off as vapor, and condenses in 'the cooler part of the 
tube, or other vessel in which the experiment is per- 
formed, as a steel grey incrustation. 

ARSENIOUS ACID. 
441. Ratsbane. — The ordinary white 

What are the _ 

properties of arsenic or the shops, also known as rats- 
ars .T™ us bane, is a white and nearly insoluble sub- 

stance, possessed of a slightly sweetish 
taste. It is not properly arsenic, but arsenious acid. It 
contains three atoms of oxygen to one of metal. Al- 
though sweet, it is called an acid because it possesses 
the chemical characteristic of an acid, viz : the ca- 
pacity of uniting with bases to form salts. 
How is it pre- 442. Preparation. — Arsenious acid i? 

lared? prepared from metallic sulphurets, many of 

which contain a certain proportion of arsenic, by 
roasting in the air, and thus burning out their arsenic in 
the form of arsenious acid. The fumes are condensed 
in high chimneys, from which the incrustation of the 
solid acid is afterward removed. Mispickel, which is 
a double sulphuret of iron and arsenic, and certain 
ores of nickel and cobalt, are much employed for the 
production of arsenious acid. 



ARSENIOUS ACID. 181 

„_ - . ._ 443. Poisonous properties of arsenic. 
What is said . 

of arsenic as White arsenic or arsenious acid is a fearful 
a poison. poison, and more frequently employed than 

any other substance, for the destruction of life. But 
its detection, and the entire demonstration of its pres- 
ence in the body, after death, or in materials which 
have previously been ejected from the stomach, is cer- 
tain. 

444. No one but a professional chemist 

What is said . . 

of its detec- should undertake such an investigation, 
Uon? involving, as it does, the issues of life and 

death. No one else, indeed, can, be qualified to guard, 
with certainty, against the presence of arsenic in the 
chemicals which are used in the process, or in other res- 
pects, to bring the inquiry to that point of absolute de- 
monstration, which is always required injudicial inves- 
tigations. But the methods of detection, being simple, 
and a subject of interesting and instructive experiment 
to the student, will be briefly described in the paragraphs 
which follow. Many other compounds of arsenic, be- 
side arsenious acid, are highly poisonous. 

How arsenic is 445. DETECTION OF ARSENIC. If a few 

detected? drops of a solution of chloride of arsenic* 

be added to the liquid from which hydrogen is being 
evolved from a vial, by the ordinary process, the 
nascent hydrogen decomposes the chloride of arsenic 
and carries off the metal in the form of a gas. On sub- 
sequently kindling the hydrogen jet and bringing 

* Such a solution is prepared by dissolving white arsenic in hydro- 
chloric acid. 




182 METALLOIDS. 

down upon it a cold white surface, like that of 
a plate or saucer, the metal is again given up, 
and reveals itself as a brownish black and high- 
ly lustrous stain. The process may be con- 
ducted in an ordinary vial, to which a pipe 
stem, or glass tube has been fitted, by the 
method before described. The above method ' 
of detection is called Marsh's test. In a case of 
suspected murder by poison, the moment of the in- 
troduction of the pure porcelain into the flame, be- 
comes one of the most intense interest. The gather- 
ing stain is at once the emblem of guilt and sentence 
Df ignominious death. 

446. Explanation. — The decomposi- 
Explamthe ^ on f arsen i us acid by hydrogen, in the 

above process. J J ° 7 

above experiment, and the reason of the 
deposition of the metallic mirror, still remains to be ex- 
plained. The nascent hydrogen affects the decompo- 
sition of the acid by a double action ; on the one hand 
uniting with the metal to form arseniuretted hydrogen, 
which escapes, and on the other hand, with its chlorine 
to form hydrochloric acid, which remains behind. The 
mirror of metal is deposited upon the plate or saucer, 
because the introduction of the cold body into the 
flame, so lowers its temperature that the metal itself can- 
not burn. If the jet of gas is left to burn without in- 
terference, both of its constituents are consumed to- 
gether, and the flame assumes a blue color, from the 
burning arsenic. 



arsenious acid. 183 

tt 447. Distinction between arsenic and 

How are ar- 
senic and an- antimony stains. — If in testing for arsen- 

l dUtmguish™ * c ? D Y ^ e method above described, a metallic 
cd - spot is obtained, the evidence of the pres- 

ence of arsenic is not entirely conclusive. A solution 
of antimony, if substituted for arsenic in the experi- 
ment, will give rise to the production of somewhat sim- 
ilar stains. But the experimenter will find, on com- 
paring the two kinds of spots, that they are of quite 
different appearance. Those of antimony are of deep- 
er black, and fainter lustre. Again, those of arsenic 
are much more readily removed by heat. " Chloride of 
soda," is a still more conclusive means of distinguish- 
ing them. A solution of this substance will dissolve 
the arsenic stains, while it leaves those of antimony 
unaffected. The " chloride of soda," to be used in 
the experiment, is prepared by adding an excess of car- 
bonate of soda to a solution of " chloride of lime," 
and then filtering the liquid. 

448. Additional tests for arsenic. — 

Mention some . 

additional A second test has already been given in 
tef ts f orars * the paragraph on the preparation of me- 
tallic arsenic, to which the student is re- 
ferred. The formation of a yellow precipitate, on the 
addition of hydro-sulphuric acid to a solution, also 
renders it highly probable that arsenic is present. 
If on drying the precipitate, and heating it with a 
mixture of cyanide of potassium and carbonate of soda, 
a metallic mirror is obtained, the inference of the pres- 
ence of arsenic is confirmed. The process is to be 
conducted as directed in paragraph 440. In this exper- 



184 



METALLOIDS. 



iment, the cyanide of potassium has the effect of retain- 
ing the sulphur, while it allows the volatile arsenic to 
pass and deposit above. 

What is said 449 ' StlU another evidence of the pres 

of the garlic ence of arsenic, is afforded in the charac 
teristic garlic odor which is emitted by ths 
flame produced by burning arsenic, in the experi- 
ment previously described, called Marsh's test. The 
same odor is also obtained on sprinkling a little ar 
senious acid upon burning charcoal. 

Mention the 450. PREPARATIONS FOR THE ARSENIC 

preparations TEST# — Before proceeding with the che 

for the ar- r o ** 

senic test? mical experiments for the detection of ar 
senic, some preliminary labor is com- 
monly required, to bring the material to 
be tested into proper form. It com- 
monly consists of matters which have 
been ejected from the stomach, or of the 
contents of the stomach itself. If the 
student wishes to begin at this point in his experi- 
ments, he may add a small portion of arsenic to 
some bread and water and proceed with this paste in 
his investigation. This mixture is to be diluted with 
water and saturated with chlorine, as in the process for 
preparing a solution of this gas. Chlorine has the effect 
of destroying a certain portion of the organic matter, 
and rendering the rest floculent, so that the liquid may 
be easily separated from it by filtration. It also brings 
the arsenic perfectly into solution, as a chloride. This 
solution is then filtered and treated as directed in tiie 
preceding paragraphs. 




CARBON. 185 

T7 . 7 , . j7 451. Antidote to arsenic. — The hv- 

WJf.rtt is the j 

antidote for drated sesquoxide of iron is regarded as 

arsenic? . , . -. /trt - <rv . , - 

the best antidcte to arsenic, (bee Oxides.) 
Its action depends on the formation of a compound 
with the poison in the stomach, which is insoluble 
and therefore inactive. Milk, sugar, and white of eggs 
are also given with advantage, as in most other cases 
of poisoning. 

452. Arsenic eaters of Austria. — 

What is said . • /• * • 

of the arsmic In the mountainous portions oi Austria, 
lria7 °^ Am ~ bordering on Hungary, the peasantry are 
given to the strange habit of eating arse- 
nic. It is said to impart a fresh, healthy appearance to 
the skin, and also to make respiration freer when as- 
cending mountains. Those who indulge in its use 
commence with half a grain, and gradually increase 
the dose to four grains. If this habit is regularly in- 
dulged, its injurious effects are said to be long retarded. 
But as soon as the dose is suspended, the symptoms of 
poisoning by arsenic immediately manifest themselves. 

CARBON. 
453. Description. — Carbon in the form 

Describe the 

different of coal, is a black, brittle, solid. As 

forms of car- pi um b ag0 an d co k e , it is grey, with me- 
tallic lustre ; as the diamond, it is trans- 
parent, and the hardest of known substan- 
ces. Plumbago is commonly called black 
lead, but it contains no lead whatever. The 
figure in the margin represents the more 
common crystalline form of the diamond. 




186 METALLOIDS. 

454. Occurrence. — In the form of bi- 

Whcrc does . -, Al , ', 

carbon occur i tuminous and anthracite coals, carbon ex- 
ists in immense quantities, buried in the 
earth, in various countries ; as graphite or plumbago, 
it is also quite a common mineral ; as the diamond, it 
is the rarest of all gems. It is one of the elements in 
limestones, marbles and chalk, which are all carbonate 
of lime. It forms nearly one half of all dried veget- 
able matter, and more than half of all dried animal 
matter. One twenty-five hundredth of the air, also, is 
carbonic acid, of which carbon is a constituent. 

455. Charcoal. — The 

Illustrate the 

preparation preparation of charcoal, one 

of charcoal q{ the forms Qf carbon? may 

be illustrated by heating a small por- 
tion of wood or cork in a test-tube. 
The other constituents of the wood, 
and part of the carbon, are converted 
into water, gases, and tar, and the larg- 
est part of the carbon remains behind in the form of 
charcoal. 

456. Preparation. — In quantity, it is 

How is char- . ■,'•■, 

coal made? commonly made by burning wood in large 
heaps^ previously covered with earth and 
sod. It is necessary to admit a little air, through open- 
ings in the heap, to maintain a partial combustion. 
If too much air is admitted, the wood is entirely 
consumed and no charcoal is produced. Coke is 
made from bituminous coal by a similar process, and 
is also obtained as a residue in the manufacture of 
coal gas. 




CARBOK. 187 

457. Lamp black. — Lamp black, still an- 
U^kmade^ other form of carbon, is made by conduct- 

ing the smoke of rosin into chambers con- 
structed for the purpose. It consists of unburned parti- 
cles of carbon. It is used, extensively, as a pigment. 
Bone black is made by heating bones in closed vessels. 
It is a sort of charcoal produced from the gelatine of 
the bones. 

458. Purifying properties of char- 

Describe the 

purifying coal. — Charcoal absorbs gases, and retains 

V Jharcol? °* tnem in its P ores > in l ar g e quantities. 
Tainted meat, and musty grain, intimately 
mixed with it, become sweet. The charcoal has re- 
moved the unpleasant gases, proceeding from them. 
The absorbent power of charcoal may be illustrated, 
by holding a paper moistened with ammonia, in a vial, 
until the air within it has acquired a strong ammo- 
niacal odor. On afterward introducing some pow- 
dered charcoal and shaking the vial, the odor will be 
removed. 

459. Preservative properties of 

Illustrate the 

preservative charcoal. — Charcoal may be used as a 
properties of preventive, as well as a corrective of de- 

charcoat ? r 7 

cay. Posts, if charred at the bottom be- 
fore they are set, are rendered more durable. Water 
will keep longer in charred vessels than in those which 
have not thus been prepared. The decay of meats and 
vegetables is retarded by packing them in charcoal. 
Charcoal is itself, one of the most unchangeable of sub- 
stances. Wheat and rye charred at Herculaneum 1800 
years ago, still retain their perfect shape. 




188 metalloids. 

., . 460. Decolorizing effects of char- 

Jj escribe its 

decolorizing coal. — Charcoal has, also, the effect of 
power, removing coloring matters, and 

bitter and astringent flavors from liquids. 
Thus, ale and porter lose both color and flavor 
by being filtered through charcoal. Sugar 
refiners take advantage of this property in 
decolorizing their brown syrups. Animal 
charcoal or bone black is best adapted to these uses. 
As an illustration of the decolorizing effect of char- 
coal, let water colored with a few drops of ink be 
filtered through bone black. . The color will be found to 
disappear in the process. 

461. Combustion of carbon. — All of 
of the com- ^e forms of Carbon are combustible. The 
bustionof combustion of charcoal in air is a famil- 

caroon s 

iar fact. Its combustion in oxygen has 
bas been already shown. The diamond and 
plumbago will also burn in a vial of oxygen 
gas, if first intensely heated. The product of 
their combustion, is precisely the same as that 
of charcoal. From the carbonic acid, which 
is produced in the combustion, the carbon 
may be obtained in the form of lamp black. The 
nature of the diamond is thus conclusively established. 
462. Reduction of ores by charcoal. 
charcoal re- The affinity of carbon for oxygen, at a 
duce metals? high temperature, is very intense. It de- 
prives most ores of their oxygen, and converts them 
into metals. An agent which thus produces metals 
from their componnds. is called a reducing agent, and 




CARBONIC ACID. 189 

the process is called reduction. Gaseous carbonic ox- 
ide has the same effect as carbon, because the affinity 
of its carbon for oxygen is only partially satisfied. In 
the process of reduction, these reducing agents are them- 
selves converted into carbonic acid, by the oxygen with 
which they combine. Hydrogen gas, in consequence of 
its strong affinity for oxygen, is also a powerful reducing 
agent. The reducing power of carbon may be illus- 
trated by sprinkling a little litharge on ignited charcoal, 
and blowing upon it at the same time, to maintain its 
heat. The litharge or oxide of lead will thus be par- 
tially converted into globules of metal. 



CARBOXIC ACID. 

463. Description. — Carbonic acid is a 

What is car- 

bonicacid? colorless gas, without much taste or smell, 
Where does it an( j a b out one an( j a jj a ]f times as heavy as 

occur f J 

air. Other properties are illustrated in the 
experiments which follow. This gas is found in many 
mineral waters, and frequently escapes from fissures in 
the earth. It is a constituent of all limestones and 
shells, and forms ^gVo part of the atmosphere. It is 
exhaled from the lungs of all animals, and is a product 
of the combustion of coal and wood. 

464. Preparation. — Carbonic acid ma\ 

How is carbo- 
nic acid pre- be prepared by burning charcoal in oxygec 

par gas, as directed in paragraph 339. Or il 

may be made by hanging a lighted candle, as long as ii 

will burn, in a bottle filled with ordinary air. I:i thu 



190 



METALLOID 



Explain the 
above process. 




case, the carbon of the candle is converted into car- 
bonic acid, by the oxygen of the air. But neither 
of these methods give the unmixed gas, and that which 
follows is therefore to be preferred. 

465. Another method. — Pour a tea- 

Give the sec- _ . 

ond method of spoonful of muriatic acid into a large- 
preparing it, mouthed half-pint vial, and then 
add bits of marble, chalk, or carbonate of 
soda until effervescence ceases. The vial 
will then be filled with carbonic acid. 

466. Explanation. — Chalk 
and marble are both carbonate of lime. 
As soon as they are dropped into muriatic acid, this 
stronger acid combines with the lime and retains it, 
setting the carbonic acid at liberty in the form of a gas. 
The gas as it accumulates, expels the air from the vial 
and completely fills it. It is obvious that in this method 
we do not make carbonic acid, but use that which na- 
ture has already made for us and imprisoned in the 
marble. 

467. For fhost of the experiments that 

Describe ano- i 

ther method of follow, the second simple method of col- 

preparahon. lection j s su ffi c i en t ; and the gas need not 

be transferred to another vessel. When 

it is desired to obtain it separate from the 

materials from which it is produced, the 

apparatus represented in the figure may 

be employed. 

468. Carbonated waters." 

How are car- 

bonated waters Water absorbs its own volume of carbonic 
** ' acid and thereby acquires an acid taste. 





CARBONIC ACJD. 191 

The so called (l soda water " or "mineral water," is 
prepared by confining water in a strong metallic ves- 
sel, and forcing into it gaseous carbonic acid, by means 
of a forcing-pump. The increased quantity which it 
is thus made to absorb is in precise proportion to the 
pressure employed. Neither of the above names give 
a correct notion of the nature of the ef- 
fervescent drink referred to. It is sim- 
ply carbonated water, to which soda is 
sometimes added. 

469. The absorption of carbonic acid 
by water may be shown, like that of 
chlorine, by the method illustrated in 
the figure. It may also be shown by pouring a gill 
of water into a half-pint vial of carbonic acid and 
then shaking it. The palm of the hand being pressed 
closely upon the mouth of the vial, the flesh will be 
more or less drawn in, to take the place of the gas ab- 
sorbed. The vial may be supported by this attach- 
ment. 

470. Effervescent drinks. — Cham- 

WJtdi l*i said 

of effervescing pagne, sparkling beer and mead, congress 
water, and similar drinks, owe their effer- 
vescent qualities to this gas held in solution. On expo- 
sure to the air, the gas gradually escapes, and the liquids 
become insipid to the taste. The air. enters and takes 
its place, expelling sixty or seventy times its own vol- 
ume of gas. This effect may be hastened by striking, 
with the hollowed palm of the hand, upon the top of 
a glass partly filled with one of these liquids ; there- 
by compressing the air, and forcing it to enter rapidly. 

9 



192 



METALLOIDS. 




(rive another 
method of per- 
forming the 
experiment 



The carbonic acid immediately escapes with renewed 
and rapid effervescence. 

471. Flame extinguished 

What effect 

\as carbonic BY CARBONIC ACID. Lower a 

acid onfamei lighted taper? candle? r Splinter 

of wood into a vial of carbonic acid, pre- 
pared as before directed. The flame will 
be immediately extinguished, as if it had 
been dipped in water. 

472. Or the same experiment may be 
performed by pouring the 
gas into a vial, at the bot- 
tom of which is a bit of 
lighted candle. Nothing will be seen 
to flow from one vessel into the other, 
but the effect will be the same as before. 
473. Carbonic acid is 

Of what use 

to plants is FOOD FOR PLANTS. — CarbOIllC 

carbonic acid? ^ {d j g Qne of the principal 

elements of the food of plants. The leaves absorb 
it from the air, and the roots from the earth, and 
convert it into wood and fruit. The subject is fur 
ther considered in the latter part of this work. 

474. It is poison for animals. — Wa- 
ter impregnated with carbonic acid is a 
healthful drink ; but the same gas, wken 
taken into the lungs, produces death. It 
operates negatively, by excluding the air, and also 
positively, as a poison. Being heavier than the air, 
lakes of this gas sometimes collect in the bottom of 
caverns. There is a grotto of this kind in Italy, called 




What is the 
effect of car- 
bonic acid on 
animals ? 



CARBONIC ACID. 193 

the Grotto del Cane, or dog's grotto. A man walking 
iii*o it is safe, but his dog, whose head is below the 
• urface of the gaseous lake, is immediately suffocated. 
Baths of carbonic acid have recently been employed, 
with advantage, in the treatment of rheumatism and 
other similar affections, and in cases of enfeebled 
vision, 

475. How removed from wells. — Car- 
bonic acid re- bonic acid often collects in the bottom of 
moved from we lls. and occasions danger, and some- 

wells ? ' d 7 

times death, to workmen employed in 
cleaning them. A candle previously lowered into the 
well will indicate the danger, if it exist. The flame 
will burn less brilliantly, or be entirely extinguished, 
if much of the gas is present. By repeatedly lower- 
ing pans of recently heated charcoal into the well, and 
drawing them up again, the gas will be absorbed and 
removed. The charcoal is first heated, to increase its 
absorbing power. In this condition it absorbs thirty- 
five times its own bulk of gas. 

476. Charcoal fires in close rooms 

How does 

burning char- Fatal accidents not unfrequently occu: 
coal cause fa- f inhaling the fumes of charcoal burned 

tal accidents? ° 

in close unventilated rooms. These fumes 
consist of mingled carbonic acid and carbonic oxide. 
The latter gas will be hereafter described. 

477. Solidification of carbonic acid. 

How may car* ^ 

bonic acid be One of the most interesting of all chemical 
solidified? experiments, is the solidification of car- 
bonic acid. By combined cold and pressure, this trans- 
parent gas, wmch, under ordinary circumstances, is so 

9 



194 METALLOIDS. 

thin that the hand, passed through it, does not recog- 
nize its presence, can be converted into a solid snow. 
This is done by bringing into a strong iron cylinder, 
conuected by a tube with a second similar receptacle, 
the material for making more of the gas than there is 
room for in the two vessels. The cylinders being 
closed, and the gas produced by the agitation of the 
materials, it is evident that they must burst, or the 
gas must pack itself away in some more condensed 
form. The second vessel is surrounded by ice, and 
kept extremely cold, during the process. In this colder 
vessel the gas assumes a liquid form. Being removed 
in this condition, one portion of the liquid evaporates 
so rapidly as to freeze the rest. An explosive expan- 
sion of the liquid into gas would naturally be antici- 
pated, but this does not occur. The materials used in 
the process are sulphuric acid and carbonate of soda. 
How is car- ^^' Oabbonic Oxide. — When carbonic 

bonic oxide acid is passed through hot coals, it loses 
* 01 half of its oxygen and becomes carbonic 

oxide. This takes place in coal fires. The coal in 
the lower part of the grate, where air is plenty, 
receives its full supply of oxygen and becomes car- 
bonic acid. The hot coals above, where the supply 
of air is limited, take half of the oxygen from the 
carbonic acid, and reduce it to this oxide, convert- 
ing themselves partially into carbonic oxide at the 
same time. The new gas passes on to the top of the 
fire, and there, where air is again abundant, it burns 
with a blue flame, and reconverts itself into carbonic 
acid. This gas is much more poisonous than carbonic 



carbonic; oxide. 195 

acid, and is one source of the danger which arises from 
open fires in close rooms. One-two-hundredth of it 
makes the air, if inhaled for any considerable time, a 
fatal poison. 

479. Combustion of carbonic oxide. 

How is car- . 

bonic oxide For small experiments, the gas is best pre- 

best prepared? ^^ by covering a half tea-spoonful of 

oxalic acid* with oil of vitriol, and heating them to- 
gether in a test-tube. The gas, on 
being kindled at the mouth of the 
tube, burns with a beautiful blue 
flame. The experiment is rendered 
more striking by producing a jet, as 
represented in the figure. The gas 
thus obtained is really a mixture of 
carbonic oxide with carbonic acid. 
but the admixture does not mate- 
rially affect the experiment. 

480. Explanation.— Eacl molecule o r 

Explain the 

formation of oxalic acid contains carbon, oxygen, a.id 
carbonic oxide. hydrogen? in the pr0 portion to form one 

molecule each, of water, carbonic oxide, and carbonic 
acid. Through the agency of sulphuric acid, this de- 
composition is effected. The water remains with 
the acid while the gases are evolved. 

481. It produces metals from oxides. 

Wltat is the 

effect on me- With the help of a high temperature, car- 

tallic oxides? ^^ oxide takeg QXfgen f ynm xidcS, 

and converts them into metals. It contains oxygen 

* This acid has the appearance of a salt, and is poisonous. 




196 METALLOIDS. 

already, but its chemical appetite is only half satisfied 
with that element. It is this gas, produced in the fire, 
as before described, which converts iron ores into metal, 
in the smelting furnace. It is itself converted into car- 
bonic acid at the same time. 

SILICON. 

What is sill-' 482. Description. — Silicon is a dark 
con ? gray substance, possessed of metallic lustre, 

but classed with the metalloids because it resembles 
thern ip its compounds. It is also called silicium. 
It is prepared from silica, by the method hereafter de- 
scribed for the production of calcium from lime. 

483. Silicic acid or silica. — Quartz 
What is ni- Qr voc ^ cr y S t a i j s nearly pure silica. Sea- 
sand, opal, jasper, agate, cornelian, and 

chalcedony, are other forms of the same substance. 
It also forms part of a very abundant class of rocks, called 
silicates, and probably constitutes one-sixth of the mass of 
the earth. 

484. Soluble silica. — Silica may be 

How can silica . . -•/»/•. 

be made solu- dissolved in water, by first fusing it with 
ble ? a large proportion of potash. On then ad- 

ding acid, to neutralize the potash, the silica precipitates 
in the form a jelly. By this circuitous process, the 
most gritty sand is converted into a soft jelly. A sin- 
gular application of this rock-jelly, in the adulteration 
of butter, has recently been detected in England. Dis- 
solved silica also occurs in nature, and hardens into 
agates, onyx, and other precious stones. 



BORON. 197 

485. Petrifactions. — As wood wastes 

What is the . . . 

cause of pet- away in certain smcious waters, the par- 
rifachon? Hcles of silica take, one by one, the place 
of the departing atoms, and thus copy the wood in 
stone. Such copies are called petrifactions. 

BOROX. 

What is bo- ^86. Description. — Boron is a brown 

ron ? powder, never seen except in the chemists 

laboratory, and of no practical value. It occurs in 
nature, combined with other elements, as borax and 
boracic acid. 

TT . , 487. Boracic acid. — This acid is coin- 

How is bora- 
cic acid form- monly seen in the form of white pearly 

scales. It exhales with volcanic vapors 
which issue from the earth in Tuscany. These va- 
pors are condensed in water, and the solid acid is 
obtained by evaporating the solution. The acid is used 
like borax, as a flux. It is bitter, rather than sour, to 
the taste, but is called an acid because it forms salts. 

HYDROGEN. 
488. Description and occurrence. — 

What is hy- . _ 

drogeni ' Hydrogen is a colorless gas, about one nf- 
Where does it teenth as heavy as the air. It is of such 

occur f J 

extreme tenuity, that it may be blown 

gold leaf and kindled on the opposite side. 

Oixe-iiiiiUi part of the ocean, and the same proportion 

of all water in existence, is hydrogen gas. It enters^ 




198 HYDROGEN. 

also, largely into the composition of all animal and 

vegetable matter, and forms the basis of most liquids. 

489. Preparation. — Introduce a few 

Describe the 

method of pre- bits of iron Or Zinc 

paring it* -^ & yial one . thir( J 

filled with water. Add a tea- 
spoon-full dt more of common 
sulphuric acid, and attach to the 
vial a bent tube or a clay pipe, ^^ 
as represented in the figure. The evolution of the gas 
immediately commences. The first portions, which 
contain an admixture of air, are allowed to escape ; the 
pipe-stem is then brought under the mouth of the vial, 
and the gas collected. # 
„ , . , 590. Explanation. — Water is compos- 

Explain the 

formation of ed of oxygen and hydrogen gases. Each 

hydrogen? wouW fce fl g& ^ but for the ^^ wMch 

holds it in the liquid form. In the above process for 
preparing hydrogen, the zinc is, as it were, the ransom 
paid for its liberation. The oxygen combines with 
the zinc and the hydrogen escapes. 

491. Pure water will not suffice in the 

What purpose 

is served by process. It must contain acid, to unite 
the acid? with the oxide of zinc, as fast as formed. 

The presence of an acid, for which the oxide has great 
affinity, seems to stimulate its formation. It may, 

* When a taper can be applied at the mouth of the pipe-stem without 
explosion, it may be certainly known that an unmixed gas is in pro- 
cess of evolution. A cloth should be thrown over the vial and this test 
made before commencing the collection. The connection of the ap- 
paratus in the above experiment is made with a paper stopper, formed 
on a bit of pipe-stem or glass tube. 



HYDROGEN. 199 

indeed, be regarded as a general law, that the pres- 
ence of acids promotes the formation of oxides, and 
vice versa. 
ri . . 492. Another method. — Hydrogen 

Give another J ° 

method of pre- may also be made by passing steam through 
paring % ^ heated gun-barrel containing bits of 

iron. Bundles of knitting needles are commonly em- 
ployed for the purpose. The steam leaves its oxygen 
combined with the iron, and escapes as hydrogen gas. 

493. Combustion of hydrogen. — Bring 
ducedby P the a dry, cold tumbler, over a burning jet of 
combustion of hydrogen. The vessel will soon become 

hydrogen ? jo 

moistened on the interior. The water 
thus produced, is a result of the combination of hydro- 
gen with oxygen of the air. But for the cold surface, 
with which it is brought into contact, it would have 
escaped into the air as vapor. The composition of 
water was shown in Part 1., (<§> 277,) by galvanic de- 
composition. It is here demonstrated by combining 
its elements and thus reproducing it. Water is also 
formed in the combustion of any substance containing 
hydrogen as one of its constituents. The above expe- 
riment may therefore be made with a lighted lamp or 
candle, as well as with the jet of pure hydrogen. 

494. Explosion of mixed oxygen and 

How is an ex- . 

plosive mix- HYDROGEN. Allow OXygeil to flow HltO an 

tureprepared? inverted via i ? as directed in para- 
graph 330, until it is one-third full. Fill it up 
with hydrogen, collected as shown in Par. 489. 
Cork the vial under water. It is now filled with 
an explosive mixture, which may be fired by the 



200 METALLOIDS. 

application of a taper. To secure against accident, the 
precaution should invariably be observed of winding 
the vial with a towel, before the discharge. 

495. Explanation. — The explosion re- 

Wln/ does this ; 

mixture ex- suits from the lact that all ox the nydrogeu 
in the vial burns at once, causing great 
heat, and sudden expansion of vapor. The combus- 
tion is thus simultaneous, because oxygen, the sup- 
porter of combustion, is present at every point. When, 
on the other hand a jet of hydrogen is kindled, no 
explosion occurs, because the combination is gradual. 
Combustible hydrogen meets with oxygen in this case, 
only on the surface of the jet. 
r, ., ,, 496. The hydrogen gun. — The expe- 

JJescrioe the r 

hydrogen gun, riment for the explosion of mixed hydro- 

and the me- , i i • 

thodofcharg- gen and oxygen gases, may be made in a 
m 9 lt - strong tin tube, provided with a vent near 

the closed end. Such a tube, about an inch in diame 
ter, and eight inches in length, is called the hydrogen 
gun. In loading it, the vent is stopped with wax, 
the tube filled with water, and the gases, previ- 
ously mixed in the right proportion, poured upward 
into it, as indicated in the figure. The 
gun, being thus loaded, is tightly 
corked, under water, and afterward 
fired at the vent. The explosion is 
sufficient to expel the cork with vio- 
lence, accompanied by a loud report. 
The vial from which the tube is loaded 
must not be too large, or it will not be practicable to 
turn it and pour upward, as desired. This difficulty 




HYDROGEN. 201 

may also be obviated, by the substitution of a water- 
pail, for the bowl represented in the figure. 

497. Charge of air and hydrogen. 

Describe an- 
other explosive As air contains uncombined oxygen, a 

mixture of air and hydrogen also forms an 
explosive mixture. But, as air is only one-fifth oxy- 
gen, five times as much of it must be used ; in other 
words, five parts of air are required, for every two 
parts of hydrogen. To make the mixture, hydrogen 
may be led, as before, into an inverted vial a little 
more than two-thirds full of air. The exact propor- 
tion is not essential in this, or any similar case of ex- 
plosive mixture. 

498. A simpler method. — A simpler 

Give a sun- . 

pier method method oi loading the gun, or charging 
°f Jading ike the vial with the exp i os i ve mixture, is to 

invert it over a jet of hydrogen, as repre- 
sented in the figure. The pipe-stem, or tube, 
which conveys the gas, is previously wound 
with paper, till it occupies about two-thirds of the 
inner space of the gun. Escaping hydrogen fills 
the remainder. On withdrawing the tube, air 
enters to take its place, and the gun is thus 
charged with mixed air and hydrogen, in the right 
proportions. It is then corked and fired. This 
experiment may also be made with a test-tube, 
discharging it at the mouth. Explosions with mixed 
air and hydrogen, are, of course, less violent than 
where pure oxygen is used instead of the diluted oxy- 
gen of the air. 

Dues hydrogen 499 # HYDROGEN WILL NOT SUPPORT COM- 

support com- . . . '■ ' . 

Wttion! bustion. — Flame is extinguished in hy- 

9* 




202 METALLOIDS. 

drogen, as it would be in water. Re-charge the gas 
bottle, if necessary, and hang a second large-mouthed 
vial above it, as represented in the figure. Af- 
ter a few minutes, it may be presumed that 
the upper vial is filled with hydrogen. Apply 
a lighted match to its mouth, and the gas will 
inflame, and continue to burn with a faint 
light. Introduce a second taper, as represent- 
ed in the figure. It will be kindled at the 
mouth of the bottle, and again extinguished 
above. The match is extinguished, because, a little 
above the mouth of the vial, there is no oxygen to sup- 
port the combustion of the carbon and hydrogen of 
which it is composed. 

500. Hydrogen made by the metal 

T/PRPVJ.hp. the 

preparation sodium. — Another very beautiful, but more 
of hydrogen expensive method of making hydrogen 
gas, is as follows. Fasten a piece of me- 
tallic sodium, of the size of a pep- 
per-corn, upon the end of a wire, and 
thrust it suddenly under the end of 
a test-tube filled with water, and held 
very near the surface, as represented 
in the figure. The metal melts as soon as it touches 
the water, and rises to the top of the tube. Hydrogen 
is immediately formed, and displaces the water, fill- 
ing the tube rapidly with the liberated gas. 
Explain the ^01. Explanation. — Sufficient heat is 

process. evolved by the action of sodium on water 

to fuse it at once. The metal is lighter than water, 
and therefore rises to the top of the~ tube. At this 




WATER. 203 

point the chemical process begins. Sodium has the 
most intense affinity for oxygen, and therefore com- 
bines with this element of the water, setting its hydro- 
gen at liberty. No acid is required as in the case of 
zinc. Metallic potassium may also be used in this 
experiment. To avoid its ignition by contact with 
the water, it is to be wrapped in paper, and the twisted 
end of the wrapper used as a holder, with which to 
thrust it under the mouth of the tube. 

WATER. 
502. Composition. — Many important 

Of what is . . ■ , , 

water com- properties oi water have already been ll- 
posed? lustrated in the chapter on Vaporization. 

Others will be mentioned below. It is composed of 
oxygen and hydrogen, as has already been proved both 
by analysis and synthesis. These gases are condensed 
in combination to about 2 oVo of their original volume. 
It remains to show how the exact proportion in 
which they enter into the composition of water is as- 
certained. 

503. First method of proof. — One 
method by gal- method is to decompose water by the gal 
V Tsititn° m ' van i c process, and collect and weigh the 
gases obtained. The oxygen is found to 
weigh eight times as much as the hydrogen. Water 
is thus shown to be composed of eight parts of oxygen, 
by weight, to one part of hydrogen. In other words, 
nine pounds of water contain 'eight pounds of oxygen 
and one pound of hydrogen. ^ 



204 METALLOIDS. 

504. Second method. — Another method 

Show how com- . 

position by is to measure the gases obtained by the 
leeightmaybc method of decomposition. Two 

calculated r 

from measure, measures of hydrogen are thus obtained for 
every single measure of oxygen. The chemist then pro- 
ceeds to calculate the relative weight. Knowing before- 
hand that hydrogen is the lighter gas, weighing but 
one-sixteenth as much as the same quantity of oxygen, 
he infers that the double volume obtained in the above 
experiment, weighs but one-eighth as much as the 
oxygen obtained in the same decomposition. The 
result of this indirect process is the same as that stated 
at the conclusion of the last paragraph. 
Describe the 505. Third method. — A third method 

third method, consists in the reproduction of water from 
mixed hydrogen and oxygen, observing at the same 
time the quantities in which they combine. This may 
be readily effected in a test-tube. The gases being 
introduced into the tube in about the right proportion, 
and in small quantity, its extremity is 
then intensely heated. A slight explo- 
sion and combination of the gases is the 
result, and the water rises to take their 
place, mingling with the small quantity 
of water produced in the experiment. Any excess of 
either gas remains uncombined. Whether this surplus 
is oxygen or hydrogen, may be readily proved by 
methods previously given. This excess being sub- 
tracted from the quantity of the same gas originally 
used, shows the proportion in which the combina- 
tion has occurred. 




WATER. 205 

506. The explosion may be avoided, 
explosion be and a gradual combination of the gases ef- 
fected, by evaporating a few drops of pla- 
tinum solution in the test-tube, and igniting the residue 
previous to the commencement of the above experi- 
ment. A ball of fine iron wire is then crowded into 
the end of the tube. The mixture of gases being 
finally introduced, the least touch of flame upon the 
end of the tube is sufficient to effect a gradual combi- 
nation. For an explanation of the agency of plati- 
num in the above experiment, the student is referred 
to the chapter on metals. The iron wire serves to 
prevent ignition, and consequent explosion, by appro- 
priating part of the heat produced by the combination 
of th3 gases. The form of the experiment last de- 
scribed, is the only one that can be recommended to 
the student. With the security against explosion 
which it affords, a test-tube filled with the mixed gases 
may be submitted to experiment. Where very accu- 
rate results are sought, the process must be conducted 
in a carefully graduated tube. By employing mercury 
instead of water, the water produced in the experiment 
may be seen. 

507. Fourth method. — Still another 

Give the meth- . . 

cd by oxide of method is illustrated in the figure. It con- 

copper. gists? essent i a i. 

ly, in the production of 
water from its elements as 
before ; furnishing, at the 
same time, the means of as- 
certaining the proportional weight of the gases which 
have taken part in its formation. The tube most 




206 METALLOIDS. 

distant from the aspirator* is first filled with oxide of 
copper, and then heated while a current of hydrogen 
gas is drawn over its surface. The heated hydrogen 
carries with it the oxygen of the copper, and passes 
into the second tube, as vapor of water. Here it is re* 
tained by potassa, or some substance of similar proper- 
ties. Both tubes are afterward weighed, and their gain 
or loss determined by comparison with their weight 
before the commencement of the process. 

508. The loss of weight in the one tube. 

How are the , > . 

results calcu- expresses the weight of the oxygen which 
lated? ^ k as f urni ; s h e cl for the formation of water ; 

the gain in the second tube, gives the weight of the water 
thus formed. The difference of the two, gives the 
weight of the hydrogen which has been appropriated 
in its passage, and now makes part of the newly formed 
water. For every nine grains of water thus produced, 
it is found that eight grains of oxygen, and one of hy- 
drogen have been consumed. Its precise composition 
is thus demonstated by another and quite distinct pro- 
cess. 

What is said 509. Solution.— Water is a very gene- 
of solution ? ra ] solvent. The disappearance of salt or 
sugar, in water, is an example. f Transparency is es- 
sential to a solution. Where the particles of a solid 
are distributed throughout a liquid, as when chalk is 



* A vessel employed, as in the present instance, to produce a current 
of air or gas, is called an aspirator. 

t Water also dissolves many gases. The ammonia of the shops is 
prepared by passing gaseous ammonia into water. 



WATER. 



207 



Wliat is pre- 
cipitation ? 




stirred with water, it is said to be diffused, instead of 
dissolved. The solvent action of water plays a most 
important part in nature, as will be seen in the conclu- 
ding chapter of this work. The subjects of solution 
and precipitation, are more fully considered in the 
chapter on Salts. 

510. Precipitation. — Where a substance 
which has been dissolved is re-converted 

into a solid form, it is said to be precipitated. 
Thus, when air from the lungs is blown 
through a pipe-stem into lime-water, the lime 
combines with the carbonic acid from the 
lungs, and falls to the bottom of the vessel, in 
the form of solid particles of chalk. The 
solid thus produced is called a precipitate. 

511. Filtration. — Filtration is 

What is filtra- 
tion, and how the separation of a precipitate 

is it effected? from %he Uquid ^ which ft ^ CQn _ 

tained. This is effected by throwing the mix- 
ture into a paper cone, which retains the 
solid, while the liquid passes through its pores. 
Such a filter is prepared by folding unsized paper into 
the shape of a quadrant, which is then opened, so as 
to form a cone, commonly supported in a glass funnel. 
It is possible, in small experiments to dispense with the 
funnel, as is done in the figure, and even to use ordi- 
nary newspaper in the place of that especially pre- 
pared for the purpose. 




208 METALLOIDS. 

512. Crystallization. — Dissolve 

How may cry* c . 

tala of alum be halt a pound oi alum in a pint of 
obtained? boiling water, and hang a cotton cord 
in the vial. As the water cools, crystals will form 
on the thread. Bonnet wire may be bent into the 
shape of baskets, miniature ships, &c. ; and cov- 
ered, by this means, with a beautiful crystalliza- 
tion. 

Explain the 613. Explanation. — Hot water has for 

process. most substances greater solvent power 

than cold water. In the case of alum, for example, water 
slightly warmed will dissolve twice as much as cold 
water. It follows, that as the hot water becomes cold, 
part of the alum must become solid again. In so 
doing, the particles, in obedience to their mutual at- 
traction, arrange themselves in crystals, as described 
in Chapter III. 

514. Snow crystals. — Snow flakes are 

What is said - 1 . . 

of snow cry s- always either grouped or single crystals, 
and their form may often be distinctly seen 
with the naked eye. They 
are best observed by catching r^N 
them upon a hat, or other ^-^ 
dark object, and inspecting them in the open air. 

515. Chemical combinations. — Water 

What is said . . 

of the combi- unites with both bases and acids, to form 
nations of wa- hydrates% Thus? NV ith lime, it forms hy- 
drate of lime ; with sulphuric acid, hy- 
drated sulphuric acid. Most of the oxveen acids in 
the form in which we employ them, contain water in 
v state of combination, and are therefore hydrated 




WATER. 209 

acids. They may also be regarded as salts, of which 
oxide of hydrogen or water is the base. 
What is mid 516. Relations to life. — Water forms, 
of water in its by f ar t | le g rea ter part of all animal and 

relations to J ° J 

life? vegetable matter, as will be more fully 

seen in the portion of this work which treats of or- 
ganic chemistry. To water, the leaf of the vegetable 
and the muscle of the animal, owe, in a great degree, 
their pliancy and freedom of motion. In view of these 
and other relations to life, the negative properties of 
water are not the least important. Had it taste or 
odor, however exquisite, we should soon weary of them. 
And but for its mild and neutral character, it would 
irritate the delicate nerves and fibres which it bathes. 
517. At very high temperatures the va- 

Whatisthe r \ . 

effect of water por of water decomposes many minerals, 
at high temp* an d eX pels strong acids from their com- 

ratures f . 

pounds. Under the stimulating influence 
of heat, this neutral liquid becomes a chemical agent 
of extreme energy. Such decompositions as are here 
referred to, are without doubt, constantly going on be- 
neath the surface of the earth. 



COMPOUNDS OF HYDROGEN, WITH CHLORINE, BROMINE, 
IODINE, FLUORINE, AND SULPHUR. 

Under this head are to be described a new series of 
acids, distinguished by the absence of oxygen from all 
which have hitherto been mentioned The molecules 
of each, like those of water, are composed of single 
atoms of their constituents. 



210 METALLOIDS. 

They are all gaseous, and are sometimes called ky~ 
dracids, from the hydrogen which enters into their com- 
position. Their salts are described in Chap. III. 

HYDROCHLORIC ACID. 

518. Description. — Hydrochloric acid 
Ifactiorw*' is a color l e ss gas, fuming by contact with 
add? What the air. It sometimes issues from volca- 

is said of its , . „ . . . 

occurrence? noes, but is, for the most part, an artificial 
product. Its solution in water is known 
as muriatic acid. 

519. Preparation. — Gaseous hydro- 
preparation* chloric acid may be produced, like water, 
by the direct combination of its elements. 
For this purpose, equal volumes of the two gases are 
mixed by candle-light or in carefully covered bottles, 
and then exposed to the direct rays of the sun. The 
action of the light is so intense, that on throwing a 
bottle thus filled from shadow into sunlight, it imme- 
diately explodes. The explosion is a consequence of 
the energetic union of the two gases, under the influ- 
ence of the chemical rays of the sun. The acid pro- 
duced is at once dissipated in the air. Great caution 
should be used in this experiment, for even the diffused 
light of day has been known, in some instances, to 
occasion explosion. 

520. Another method. — Hydrochlori 

Describe an- 
other mode of acid may also be made from common salt. 

preparing it? w hi c h furnishes the chlorine, and ordinary 
hydrated sulphuric acid, which furnishes the hydrogen. 



HYDROCHLORIC ACID. 



211 




A tea-spoonfull of common salt is introduced into a 
test-tube with about the same 
bulk of water. Half as much 
acid is added, the mixture then 
gently heated, and the acid gas 
ied into water, as shown in the 
figure. Water absorbs, at ordi- 
nary temperatures, 480 times 
its own volume of the gas. 
There is no occasion, for the 

purpose of experiment, to carry on the process till it is 
thus saturated. A few minutes will suffice to make an 
acid strong enough to dissolve zinc. 
Explain the 521. Explanation. — Hydrated sulphu- 

process. r j c ac j ( j k as a i wa y S a strong tendency to 

form metallic salts. In this case it takes the metal, 
sodium, from the common salt, and thereby converts 
itself into sulphate of soda. At the same time it gives 
back hydrogen to the salt, in place of its lost sodium, 
converting it, by the exchange, into hydrochloric acid. 
The process just described, is the one always employed 
in the manufacture of hydrochloric acid. 

522. Action of hydrochloric acid on 

What metals . . ' . 

does hydro- metals. — Hydrochloric acid dissolves tin 
chloric dis- an( j a jj f ^\e metals which precede it in 

solve ? r 

the chapter upon metals. For tin, a hot 
and concentrated acid must be employed. 

523. The solution depends on the fact 

On ivhat does 

the solution that the metals take chlorine, from the 
depend? hydrochloric acid, thereby converting 

themselves into soluble chlorides. The hydrogen then 



212 METALLOIDS. 

assumes ihe gaseous form, and escapes with lively ef- 
fervescence. An experiment may best be made with 
zinc, covered with a little dilute acid. 
What is aqua 5 24. Aqua regia. — On mixing nitric 
rcgia? ac j(j w j t h half f its bulk of strong hydro- 

chloric acid, aqua regia is produced ; so called, from its 
regal power over the noble metals. Gold and platinum, 
which are not effected by either acid alone, dissolve 
readily in aqua regia. The solvent power of aqua re- 
gia depends, as before explained, on the nascent chlo- 
rine which it supplies. 

525. Hydrobromic and hydriodtc acids. 

KIS These acids are of interest to the chemist 

hydriodic only. They resemble hydrochloric acid, 

in being colorless gases, oaongly acid, 
soluble in water, and capable of dissolving many 
metals. 



HYDROFLUORIC ACID. 

526. Description. — Hvdrofluoric acid 

What is hy- . J 

drofJuotic is a colorless, corrosive gas, acting on glass, 

and many minerals which other acids do 
not affect. It condenses into a liquid at the freezing 
point of water. It is not known to occur ready formed 
in nature. 

527. Preparation. — Hydrofluoric acid 

How is hydro- . r . , ■ _ ._ 

fluoric akd is made irom a mineral called fluor spar. 
prepared? ^ ^ same mea iis employed to make hy- 
dochloric acid. On account of its corrosive action on 
glass, vessels of lead or platinum are employed in the 



HYDROFLUORIC ACID. 213 

process. This gas is so poisonous, when inhaled, and 
its solution so corrosive to the skin, that its prepara- 
tion, in any considerable quantity, should be left to the 
experienced chemist. 

Explain the 628. Explanation.— In the above pro- 

process ? cess ^ the fluor spar, which is a fluoride of 

calcium, furnishes the fluorine, and hydrated sulphuric 
acid, the hydrogen. The remaining constituents unite 
to form sulphate of lime, which remains in solution. 

529. Etching on glass. — It has already 

Crivp the T)YO~ 

cess for etch- been stated that hydrofluoric acid attacks 
ing glass. glass and many minerals. By covering 

with wax, they may be protected against the corrosion. 
Advantage is taken of these two facts in etching 
upon glass. The surface is first slight- 
ly warmed and rubbed with beeswax, ^^Rg ^^y 
and then warmed again, to produce an 
even coating. Figures or letters are 
then drawn upon the glass, through the wax, with 
a pen-knife or other pointed instrument. The plate 
being now exposed for a few minutes to the fumes 
of hydrofluoric acid, and the wax subsequently re- 
move i, is found to be deeply etched. Fumes of hy- 
drofluoric acid for the purpose, are best obtained by 
placing a half tea-spoonful of pulverized fluor spar 
in a warm tea-cup, and covering the powder with oil 
of vitriol. A little ether or potash will be found of 
use in removing the last portions of wax from the 
plate. 

Explain i/ie ^30. EXPLANATION. As OXygeil COIli- 

above process. \ ) \ nes with carbon to form carbonic acid, so 



214 METALLOIDS. 

the hydrofluoric acid eats out the silicon of the glass, 
where it is exposed, and passes off with it, in the form 
of a new and more complex gas. A solution of the 
gas may be prepared by the process employed for hy- 
drochloric acid. Bottles of vulcanized India rubber 
or gutta purcha may be used in keeping the solution 

HYDROSULPHURIC ACID. 
531. Description — Hydrosulphuric acid 

Whatishy- . / ■ r l 

drosulphuric is a colorless gas, also known as sulphu- 
a retted hydrogen. It has a putrid odor and 

feeble acid properties. Like the rest of the series, it 
is soluble in water. It occurs in many natural waters, 
called sulphur springs. It is one of the products of 
the decomposition of animal matter, and the source of 
much of the disgusting odor which they emit during 
putrefaction. 

How is it pre- 532. Preparation. — It is made from 
pared? sulphuret of iron, as hydrochloric acid 

is made from common salt, and hydrofluoric acid 
from fluor spar. In the above process, sulphuret 
of iron furnishes the sulphur, and hydrated sul- 
phuric acid, the hydrogen. The remaining elements 
unite to form sulphate of iron, which remains in solu- 
tion. On account of the disgusting smell of the gas, 
it is best to prepare it only in small quantities. 

533. Discoloration of metals and 
has it 6n met- paints. — The blackening of silver watches 
als t dec. 9 an( j co i ns? i n t h e vicinity of sulphur 



IIYDROSULPHURIC ACID. 215 

springs, is an effect of hydrosulphuric acid gas. Its 
discoloring effect may be illustrated, by pouring a little 
dilute sulphuric acid upon a few grains of sulphuret of 
iron, in a tea-cup, and holding a bright moist coin in the 
fumes. Its effect on paints may be shown by exposing 
a piece of paper, moistened with solution of sugar of 
lead, in the same manner. The white paper immedi- 
ately assumes a dark metallic stain. Paper moistened 
with a solution of tartar emetic, takes a deep orange hue. 
This experiment is often varied, by drawing amusing 
figures on paper with lead solution, and bringing them 
out by exposure to the gas. 

534. Explanation. — The change of 

Explain the , . . . _ „ 

cause of the color in each case, is owing to the forma- 
itlor 960 ^ t * on °^ a meta Ui c sulphide, having a diffe- 

rent, and generally a darker color. Zinc 
is not blackened, because its sulphide happens to be 
white. For this reason, chemical laboratories and other 
places where hydrosulphuric acid is likely to be evolved, 
should be painted with zinc paints, instead of those 
containing lead. 

535. Relations to life. — Sulphuretted 

What is the 

effect of ml- hydrogen, if inhaled in any considerable 
drogL o/i an- quantity, acts as a poison. Caution should 
imals? therefore be observed in experiments with 

this gas. The mixture of gases which is given off 
from recently ignited coal, contains sulphuretted hy- 
drogen acid in large proportion, and owes its deleterious 
qualities, in considerable part, to this admixture. 



10 



216 METALLOIDS. 



AMMONIA. 
_ . 536. Description. — Ammonia is a col- 

What is am* 

monia? orless gas, of pungent smell, and alkaline 

^ur 6 ? d ° eSit P r °perties. It is exhaled from valcanoes, 
and is a product of the decomposition of 
all vegetable and animal matter. Its molecule contains 
one atom of nitrogen to three of hydrogen. 
vr , , . ., 537. Production from its elements. 

I vhat is said 

o/itsproduc- Although nitrogen and hydrogen gases are 
tr^mrnidhy- the s °l e elements of ammonia, they cannot, 
drogen? under ordinary circumstances, be made to 

unite directly and form it. Heat does not stimulate 
their affinities sufficiently to bring about this result- 
Electrical sparks passed, for a long time, through a 
mixture of the gases, cause them to combine to a lim- 
ited extent. 

_ . 538. Production from nascent ele~ 

Production . 

from its nas- ments. — Iron, at a high temperature, ex- 
cent elements. pe j s hydrogen from ordinary hydrate of 
potassa, and nitrogen from nitre. If heated with both 
together, it expels both nitrogen and hydrogen, and the 
two nascent elements unite, to form ammonia. The 
experiment may be performed by covering bits of potash 
and nitre with iron filings, and heating them in a test- 
tube. Another method of producing ammonia, through 
the agency of platinum sponge, is described under the 
head of Platinum. 
„ . 539. Preparation. — Ammonia is eom- 

How is ammo- 
nia co?nmon- monly made from salts that contain it, by 

yp e P a7 using some strong base to retain the acid, 



AMMONIA. 



217 




and set the gas at liberty. Potash or lime may be 
used for this purpose. Introduce into a test- 
tube about half au inch of a stick of fused potash, 
and cover it with powdered sal-ammoniac. 
On the addition of water to dissolve them, am- 
monia will be immediately evolved. Rest the 
tube on the table, and place a wide-mouthed 
vial over it to collect the gas. 

540. Solution in water. — Aqua ammo- 

tfow is its sv- 

lability in wa- nle. Bring the mouth of the vial filled with 
ter proved? amtnoniacal gas, quickly, into a bowl of 
water. The water will swallow up the gas so rapidly as 
to rise and fill the vial, producing a weak solution of 
ammonia or hartshorn. If only a small portion of 
water be allowed to enter, and the vial be then re- 
moved from the bowl and shaken, the hartshorn ob- 
tained will be comparatively strong. For the prepara- 
tion of th.e solution in large quantity, the method given 
in the section on Chlorine is to be preferred. The 
vial should be previously warmed. Newly slaked lime 
may be substituted for potash. 

How may the 54L A MINIATURE FOUNTAIN.— Fill a 

ammonia be pint vial with ammonia, by 

employed to . 

produce a jet the method above given, and 
of water? immediately introduce, air- 
tight, into its mouth, a moist paper 
stopper with a bit of pipe-stem run 
through it. Then invert the bottle into 
a bowl of water. The absorption by 
the first portions of water that enter will be so com- 

10 




218 METTALLOIDS. 

plete as to produce a vacuum, into which more wa- 
ter will rise, in a jet, as represented in the figure. 

542. Alkaline properties. — Bring the 

Explain its 

action on material for making ammonia into a tea- 

acids. CU p Qr s j m j[[ ar p en vessel. Hold a strip 

of litmus paper, previously reddened by an acid, in the 
gas, as it is evolved. The acid will be neutralized by 
the ammonia, and the paper restored to its original color. 
Any substance which is very soluble and neutralizes 
strong acids, is called an alkali. As ammonia has this 
property, and is also volatile, it is therefore called a vol- 
atile alkali. The same experiment with litmus paper, 
may be also made with the hartshorn obtained in the 
last experiment. 

543. It fumes with acid vapors. — 

Describe its 

effect on acid Moisten a piece of paper with strong mu- 
vapors. riatic acid, and wave it to and fro through 

the gas. White fumes are produced, by the 
union of the muriatic acid and the ammonia. 
In uniting, they form small particles of mu- 
riate of ammonia, or sal-ammoniac, in the air. 
It is of these that the fumes consist. It will 
be observed, that in this experiment the ma- 
terial from which the ammonia was originally pre- 
pared is reproduced. The same fumes are formed 
on waving a paper moistened with muriatic acid through 
the atmosphere of a stable. Ammonia is constantly 
evolved in such places, from the decomposition of ani- 
mal matter. 




PHOSPHURETTED HYDROGEN. 219 

PHOSPHURETTED HYDROGEN. 
544. Description. — Phosphuretted hy- 

Wlixt isphos- -ii 

phurettedhy- drogen is a colorless gas. of an odor that 
drogcn? j ms been compared to that of putrid fish. 

It is spontaneously inflammable by contact with the 
air. In the relative proportion of its elements, it cor- 
responds with ammonia. This gas is sometimes pro- 
duced in the decay of vegetable and animal matters. 
The jack-o-lanteni, or will-o-the-vnsp, sometimes seen 
in swamps and grave-yards, is supposed to have its 
origin in the spontaneous production and combustion 
of this gas. 

How is it pre- ^45. Preparation. — Phosphuretted hy- 
paredi drogen is made from phosphorus, with the 

help of water and an alkali. Water furnishes the requi- 
site hydrogen, if lime or potash is at the same time 
present. Introduce into a small vial two-thirds full of 
water, a stick of ordinary fused potash, broken in pieces, 
and a bit of phosphorus of the size of a pea. On the 
application of heat, this gas is evolved. It is carried 
through a pipe-stem, and al- 
lowed to bubble up through 
water contained in a tea-cup 
or bowl, as represented in the 
figure. If the atmosphere is 
still, the bubbles, as they burst 
and inflame, form beautiful 
white rings, which rise in succession into the air. 
These rings consist of particles of phosphoric acid, 
produced by the combustion of the phosphorus which 




220 METTALLOIDS. 

is contained in the gas. In order that the gas may be 
safely evolved, it is best to heat the vial in a tea-cup 
containing salt dissolved in three times its bulk of 
water. The addition of salt has the effect of raising 
the boiling point. The comparatively high tempera- 
ture required, may thus be obtained without exposure 
of the vial to the direct flame of a lamp. 
Explain the 546. Explanation. — In the action which 
above process, occurs in making phosphuretted hydrogen 
from potash, water, and phosphorus, the latter plays 
the part of an extremely rapacious element. It makes 
no distinction in the objects of its appetite, but seizes 
upon both oxygen and hydrogen of the water, two 
substances as widely different from each other as pos- 
sible. It forms with the one, phosphuretted hydrogen, 
and with the other, what might be called phosphuret- 
ted oxygen, but is, in fact, an acid. Potash is em- 
ployed in the process, to promote the formation of this 
acid. In its absence, water resists the affinities of the 
phosphorus, and neither acid or phosphuretted hydro- 
gen are obtained. 

COMPOUNDS OF HYDROGEN WITH CARBON. 

547. Most of the compounds of carbon and hydro- 
gen belong to the vegetable world, and will therefore 
be more properly considered in the chapter on organic 
chemistry. Only two of them, which exist ready 
formed in nature, will be here mentioned. 



CARBURETTED HYDROGEN. 



221 



LIGHT CARBURETTED HYDROGEN. 



What is light 548 ' Description.— Light carburetted 
carburetted hydrogen is a colorless, inodorous, in- 
Where^oes it flammable gas, about half as heavy as 
occur? a j r j ts mo lecule contains two atoms of 

carbon to four of hydrogen. It is produced in ponds and 
marshes, by the decomposition of vegetable matter under 
water, as will be more fully explained in Part IV. From 
this circumstance it is also called marsh gas. Mixed 
with other gases, it issues from fissures in coal mines, 
forming the fire da7np formerly so much dreaded on ac- 
count of its explosive properties. As coal is of vegeta- 
ble origin, the gas of the mines which proceeds from 
it is also traceable to the vegetable world. In some 
districts, and more particularly in regions where 
borings are made for salt, it issues from the earth in 
sufficient quantity to form the fuel which is required 
to boil down the brine, or even to illuminate villages. 
549. Preparation. — An 
impure, light carburetted hy- 
drogen, is obtained from wood by simple 
heating. For this purpose, saw-dust or 
bits of shavings are heated in a test-tube. 
The gas may be burned in a jet as fast as 
formed. The product thus obtained is 
not pure, but mixed with olefiant and 
other gases which make the flame more 
luminous. The pure gas may be made 
^rom strong vinegar, (acetic acid,) by the agency of 
heat and potash, as will be explained in the latter part 
of this work. 



How is it pre- 
pared ? 




222 METTALLOIDS. 

550. Explosions in mines.— Marsh gas 

Explain the 

cause of explo- forms, with air,an explosive mixture be- 
ihninmines. fore alluded to? which ]s often the occa . 

sion of fearful accidents in mines. The experiment 
may be made with olefiant gas, which has the same 
explosive property. This property belongs, indeed, to 
most gases and vapors which contain hydrogen ; as for 
example, to the vapors of ether, alcohol, camphene, 
and " burning fluid." 

551. Davy's safety lamp. — The dis- 

Descrioe Da m 

vy's safety tinguished English chemist, Davy, devised 
lamp. a j^g^Qd f security against these explo- 

sions. It consists in surrounding the 
miners' lamp with wire gauze, which 
will admit air through its insterstices, 
but will not let out flame to ignite the 
explosive atmosphere of the mine. 
This effect may be illustrated, by 
holding down a piece of Avire gauze upon the flame of 
a candle. If the gauze is fine, the flame will not 
pass through it. This effect is owing to the reduc- 
tion of temperature which the wire occasions. The 
subject will be better understood by reference to the 
paragraphs which follow, on the nature of flame. 



HEAVY CARBURETTED HYDROGEN. 

552. Description. — Heavy carburetted 

What are the 

properties of hydrogen is a colorless gas, of peculiar 
olefiant gas i swee ti s h odor, also kno wn as olefiant gas. 




CARBURETTED HYDRCGEN. 



223 



It is nearly twice as heavy as the light carhuretted hy- 
drogen just described, and contains twice the quantity 
of carbon. It forms a small proportion of the Jire 
damp of mines and salt borings, before described. 
How is it pre- 553. Preparation. — Heavy carburetted 
pared? hydrogen is made from alcohol, by the de- 

composing action of sulphuric acid. Bring into a test- 
tube a tea-spoonful of alcohol, with a little sand, and 
add four times as much oil of vitriol. On heating over 
a spirit lamp, the gas is evolved, and may be burned 
like the gas just described, at the mouth of the tube. 
The acid employed has the effect of retaining part of 
the elements of the alcohol, and allows the rest to 
escape as olefiant gas. The reaction* is more fully ex- 
plained under the head of organic chemistry. 
rr . .„ 554. Illuminating gas. — Gas for illu- 

How is illu- 
minating gas ruination is commonly prepared from bitu- 
minous coal. Such coal is principally 
composed of carbon and hydrogen. A portion of 
these elements pass off under the influence of a high 
temperature, in the form of gas. The product is 
rather a mixture of gases, among which light and 
heavy carburetted hydrogen are the principal. The 
process may be illustrated, by heating a little pulver- 
ized bituminous coal in a test-tube. If the heat is in- 
tense, coal tar will be produced at the same time. The 
illuminating power of gas is principally derived from 
heavy carburetted hydrogen. Its quality, within cer- 
tain limits, depends on the relative proportion of this 
constituent. 

* The term reaction, signifies, in chemistry, the mutual action oi 
chemical agents. 




224 METALLOIDS. 

How is it pic- 555. Purification. — The gas as it rises, 
rificdt contains ammonia and sulphuretted hydro- 

gen, two impurities which it is essential 
to remove. The first may be stopped 
in its passage, by a loose wad of moist- 
ened paper ; the last, by a similar wad, 
moistened with solution of sugar of lead. 
The papers having been introduced, the 
pipe-stem is fitted to the tube with a pa- 
per stopper, and the tube heated over the 
alcohol flame with the help of a blow-pipe. When 
the coal has become red hot, the gas will pass off in 
sufficient quantity to be ignited at the extremity of 
the tube. 

556. At the conclusion of the process, 

How are the r 7 

impurities the upper wad contained in the tube will 
be found blackened by the sulphuretted 
hydrogen which it has retained. On removing the 
second one, it will be found to smell of ammonia. The 
presence of this body may also be shown, by the fumes 
which it yields with muriatic acid. 

557. Arrangements in gas works.-— 

Describe tlte 

process in gas The process in gas works is essentially the 
works - same, as that above described. The coal 

is heated in iron retorts. The tar collects in pipes lead- 
ing from it. Carbonate of ammonia is washed out by 
a jet of water, which plays in an enlargement of the 
pipe. Lastly, sulphuretted hydrogen is removed by 
the retentive power of a metallic base, lime being gen- 
erally substituted for lead. 




FLAME. 225 

558. Collection and distribution.— 

nZnlfascol After purification, the gas is collected in 
lectedand dis- large iron holders called gasometers. 

tributed? & fe 

These may be represented by the inverted 
tumbler of the figure. Gas pouring 
in from below would lift and fill it. 
If an orifice were made in the top, 
the tumbler would immediately set- 
tle into the water. The air would, 
at the same time, escape through the 
orifice. The distribution of illumina- 
ting gas, from public gas works, is effected on the 
same principle. The weight of the sinking gas- 
ometer, is sufficient to press it through pipes, to all parts 
of a large city. 

559. Gas from wood. — Gas may be 

How may 9^ r 

be made from made from wood by the same means 
above given. Only a moderate heat is re- 
quired, in this case, to produce tar at the same time. 
Gas of higher illuminating power than that prepared 
from wood or coal may also be made from oil fat or 
rosin. Even refuse vegetable substance may be em- 
ployed. A pound of dried grape skins have been found 
to yield 350 quarts of excellent illuminating gas. The 
dried iiesh of animals has sometimes been used for 
its manufacture. 

FLAME. 

What is ^id &§Q. Flame.— Nothing in nature is, to 
of fiamt ? t j ]e uninstructed eye, more mysterious than 
flame. It is, seemingly, body without substance, and 

1.0* 



226 



METALLOIDS. 



shape, without coherence. It is created by a spark, 
and annihilated by a breath. Invulnerable itself, it 
destroys whatever it touches. Divided and subdivided, 
it is still the same, yet endowed with the power of re- 
solving other materials into their elements. Chemistry 
resolves this mystery, and gives us the satisfaction of 
definite knowledge in its place. But, as in all similar 
cases, while satisfying the understanding, it opens new 
fields to the imagination. The subject of combustion, 
as involved in flame, introduces us, for example, to a 
knowledge of the grand system of circulation of mat- 
ter as set forth in the last chapter of this work. 
_ , . , 561. Structure of flame. — Explana- 

£iX plain the 

structure of tion. — Every lamp or candle, is 
fi ame ' a gas factory, in which gas is 

first produced out of oil or fat, by the fire 
which kindles it, and afterward by the heat 
of its own flame. A flame, if carefully ob- 
served, will be found to consist of three 
distinct parts ; a dark centre, a luminous 
body, and a faint blue envelop. The dark 
centre is unburned gas. The body of the 
flame consists of particles of carbon or lamp- 
black, heated white hot by the combustion 
of hydrogen. In the exterior blue envelop, 
the carbon particles are consumed as they 
are crowded outwards by the flow of newly-formed 




562. Effect of flame on metals.— 
tffect of flame If a tarnished penny be held perpendicu- 

on metals? j ar j y in the flame of ft kmp Qr ca ndle, the 



FLAME. 227 

portion within the flame will lose its coating of oxide, 
while the exterior portions at the same time become 
more deeply oxidized, and consequently, darker colored. 
It is because there is an excess of carbon and hydro- 
gen in the interior of the flame, to take oxygen from 
the metal, by their superior affinity, and pass off with 
it as gas or vapor. In the outside, on the other hand, 
there is an abundant supply of air to impart oxygen, 
or, in other words, to oxidize. By moving the coin to 
and fro after it is once thoroughly heated, the instanta- 
neous conversion of metal into oxide, and oxide into 
metal, may be readily observed. A beautiful play of 
colors, like those upon a soap bubble, will be found to 
attend the transformation. The flame of a spirit lamp 
is, in some respects, preferable for this experiment. 
„„ . T 563. Oxidizing flame. — The blue en- 

What is the 

oxidizing velop of the flame, which, with the hot 

flame i a j r a( jj a cent, h as t h e property of oxidizing 

metals, is called the oxidizing flame. 
„„ , 564. Reducing flame. — The body of 

What is the . 

reducing the flame, which, with the heated gas 

flame ? within it, has deoxidizing effects, and re- 

duces oxides again to the metallic form, is called the 
reducing flame. The process of deoxidizing is called 
reduction. 

565. The blow-pii^e. — The peculiar 

blow pipe of effects of both the oxidizing and reducing 

■ ™ n f l f m con - flame, may be still better obtained by help 

structton. J J r 

of the simple mouth blow-pipe. In want 
of a metallic tube, a common tobacco-pipe, to the bowl 



228 METALLOIDS. 

of which a piece of a second stem is fitted, 

as represented in the figure, may be made 

to answer the purpose. With its aid, a 

lamp or candle flame is converted into a 

miniature blast furnace. The mouth is ap-^ 

plied at the end of the long stem, while 

the shorter one carries the blast to the flame. The 

orifice of the latter should be extremely small. It 

may be so rendered, by filling with clay and then 

piercing it with a needle. 

566. Oxidizing blow-pipe flame. — To 
SZ-pip^used oxidize with the blow-pipe, the flame, 
for oxidation? mixed with a large proportion of oxygen, 

Give an ex- . _ . _ . , , . 

ample. is blown forward upon the metal, or other 

material, subjected to experiment. This is 
effected by introducing the extremityof the blow-pipe, 
a little within the flame. 
The air of the lungs be- 
comes thus mixed with 
the rising gases. The 
result is a slender, blue 
flame, at the point of 

which, within its fainter blue envelop, the metal is 
to be held. A piece of lead, of the size of a grain of 
wheat, placed on charcoal, hollowed out for the purpose, 
and exposed to the flame, will soon be converted into 
litharge. The oxide will be recognized by the yellow 
incrustation which it forms upon the charcoal support 

567. Reducing blow-pipe flame. — To 

How is the . ' . 

blowpipe used convert oxides into metals, or in other 

f Zt r auT iUg WOrds > t0 redaCe With the aid ° f the 

blow-pipe, the gases of the flames are 




FLAME. 



229 




blown forward, upon the substance, mixed with little 

air. The extremity of 

the blow-pipe is placed 

against the outer wall of 

the flame, a little higher 

than in the previous case. 

The flame thus produced 

is yellow, and of the shape represented in the figure. 

The oxide to be reduced, is to be placed within the 

yellow body of the flame, but near its termination. 

The litharge produced in the last experiment, may 

be re-converted, by this means, into metallic lead. 

568. OXYHYDROGEN BLOW-PIPE. The 

compound or oxhydrogen blow-pipe, as 

commonly constructed, consists of two 

gasometers, containing, the one, oxygen, 

other hy- 



D escribe the 
oxyhydrogen 
blow-pipe. 



and the 

drogen gas. Tubes 
leading from these, 
are brought together 
at .their extremity, 
and the. two gases are 
burned in a single jet. 
The heat thus pro- 
duced, is the most in- 
tense that has ever 
been realized except 
by galvanic means. Iron, copper, zinc, and other metals, 
melt and burn in it readily ; the former, with beau- 
tiful scintillators, and the latter, with characteristic 
colored flames. With a sufficiently constant flame 

10* 




230 



METALLOIDS. 



platinum also may be readily fused. The apparatus 
represented in the figure, furnishes a simpler means of 
obtaining similar results. An abundant flow of hy- 
drogen is required, and a pint bottle should, therefore, 
be employed in its preparation. To retain it free from 
water, which would tend to reduce the heat of the 
flame, a little cotton may be introduced into the bowl 
of the pipe through which it passes. In evolving the 
oxygen, only a part of the tube should be heated at a 
time lest the gas should be too rapidly evolved. 

Flame continued. — The student will 

How isthena- ., , 

ture of flame already have found abundant evidence that 
{Zted 1 ? 111 ™' a * r or ox yg en is essential to combustion. 
A still more striking illustration of the sub- 
ject remains to be given. A phosphorus 
match, if suddenly introduced into the 
interior of a flame, notwithstanding the 
high temperature in its vicinity, is not 
ignited. The wood burns off, but the 
phosphorus of the match does not un- 
dergo combustion. The same principle 
may be illustrated by holding a match 
for a moment through the body of the 
flame. It is consumed at the sides, 
while the centre remains unburned. 




CLASSIFICATION OF METALS. 231 

CHAPTER II. 

METALS. 

569. Classification. — The metals may 

How may the 

metals be das- be arranged in groups or classes, according 
sified? tQ their a fg n i t y f or oxygen. Those which 

tarnish or rust most readily, come first in order, while 
the last group is made up of the noble metals, which 
retain their brilliancy unimpaired. 

570. Class i. Potassium and sodium. 
metals of These two metals combine with oxygen so 
Class I. eagerly, as to tarnish instantaneously on 
exposure to the air. They even seize on that which 
is contained in water and expel its hydrogen. The 
hypothetical metal ammonium, is described in connec- 
tion with this group, because of the similar properties 
of its compounds. 

Describe Class ^71. CLASS II. BARIUM, STRONTIUM, CALCI- 

n - um, magnesium. — The metals of this class 

show their affinity for oxygen in the same manner as 
those of Class I. But they are inferior, in this respect, tc 
both potassium and sodium. Either of these metals 
can deprive them of the oxygen with which they may 
have combined. 

Describe Class 572. CLASS III. MANGANESE, ALUMINIUM, 
"^ IRON, CHROMIUM, COBALT, NICKEL. The 

metals of this class tarnish less rapidly than the fore- 
going, by exposure to the air. In order that they may 
decompose water, and appropriate its oxygen, they re- 



232 METALS. 

quire the stimulus of an acid, or of heat. Except in 
the case of manganese, the heat must be sufficient to 
convert the water into steam. Strictly speaking, there- 
fore, they do not decompose water, but steam. 

Describe Class ^73. CLASS IV. TlN AND ANTIMONY.— 

IV- Tin and antimony tarnish less readily than 

the metals of the previous class. To enable them to 
decompose water, and appropriate its oxygen, they re- 
quire the stimulus of a red heat. An acid, or mode- 
rate heat will not suffice. 

Describe Class 57 4. CLASS V. COPPER, BISMUTH, AND 

v - lead. — Although copper and lead become 

tarnished, or covered with a thin film of oxide, rather 
more readily than the metals of the last two groups, 
their affinity for oxygen under other circumstances is 
less. This is evident in the fact that a red heat ena- 
bles them to decompose water and appropriate its oxy- 
gen but feebly. Acids will not suffice. Bismuth 
does not tarnish so readily as copper or lead. 

Describe Class 5 ^5. CLASS VI. MERCURY, SILVER, PLA- 

VL tinum, and gold. — The metals of this 

class do not tarnish, and do not decompose water under 
any circumstances. Even if made to combine with 
oxygen by other means, they yield it again very readily, 
and return to the condition of metals. They are called 
the noble metals. 



POTASSIUM. 233 

CLASS FIEST. 

POTASSIUM. 

576. Description. — Potassium is a 

dcTriptiT?^ bluish white metal > Jigger than water, 
solvents; and soft, like bees-wax. Like wax, it is 

occurrence? _ _ 

also converted by the heat of an ordinary 
fire into vapor. Water and acids dissolve it readily. 
The metals of this and the following groups, were dis- 
covered by Sir Humphrey Davy, early in the present 
century. They were first produced by the galvanic 
process. Potassium is a constituent of many rocks, 
of all fertile soils, and of the ashes of plants. The 
more important minerals which contain it, are men- 
tioned in Chapter III. 

577. Preparation. — Potassium is made 

Hew is potas- . 

slum pre- from carbonate oi potassa, by removing 

pared? ^ g car ] DOn J c ac j(j anc l ox- 

ygen. This is accomplished by 
heating intensely with charcoal, which 
removes both in the form of carbonic oxide. 
The metal which accompanies the gas, in the form 
of vapor, is condensed by naptha, instead of water. 
The process is essentially the same as that for preparing 
phosphorus, but requires apparatus beyond the reach of 
the ordinary experimenter. Cream of tartar, if heated, 
is converted into a nearly suitable mixture of carbonate 
of potassa and pure carbon, for this purpose. A small 
quantity of charcoal, in fragments, is added, and the 
whole heated intensely in an iron retort. 




234 METALS. 

Explain the 578. COMBUSTION ON WATER. Potas- 

actionofpo- s i um if thrown upon r?£^n 

tassium on _ r ■■ S'/j^'r 

water. water, is immediately ^^_^ &^^ _ _ 

ignited and burns with a beautiful ^^ifiiisis^^- 
violet flame. Strictly speaking, it is not potassium 
which burns, but the hydrogen which it sets at liberty, 
Owing to its strong affinity for oxygen, it takes this 
element from water, liberating, and 'at the same time 
kindling, the hydrogen with which it was before 
combined. The color of the flame is due to a small 
portion of vaporized potassium which burns with 
this gas as it is evolved. The globule of metal used 
in this experiment gradually disappears, because the 
potassa which it forms by uniting with oxygen is 
soluble in water. 

579. Uses of potassium. — Potassium 

State the uses ».«■■• 

of potassi- has not been applied to important uses in 
the arts, but is a valuable agent in the 
hands of the chemist. It is a key which unlocks 
many substances from the prison in which nature has 
confined them. Through its agency, brilliant metals 
may be obtained from lime, magnesia, and common 
clay. 

580. This effect depends on the supe- 

On what does . . . ,, 

its action dc- nor affinities of potassium, which enable 
pcnd? - t tQ a pp r0 p r iate oxygen, chlorine, and 

other substances, with which the above and several 
other metals are combined in nature, and to isolate the 
metals themselves. The potassium is at the same 
time converted into oxide or chloride of potassium, 



sodium. 235 

both of which are soluble in water, and may be washed 
away from the metal which has been produced. 

SODIUM. 
„ _ 581. Properties. — The metal sodium is 

Sodium — de- 
scription, similar in its properties to potassium. It 

MlveZtf l an'd * s P re P are( ^ ^Y similar means, from carbo- 
occurrcnce ? nate of soda, and may be employed by the 
chemist, for the same purposes. It occurs, principally, 
in nature, in the form of common salt. Thrown upon 
water, it decomposes it, without however igniting the 
hydrogen which is evolved. * Sodium is readily sol- 
uble either in water or acids. 

582. Uses of sodium. — Sodium is now 

For what pur- . . . . 

pose is it prepared in large quantities, in France, 

as a material to be used in the manu- 
acture of the metal aluminium.. Its cost, a few years 
since, was ten dollars an ounce. It can now be pro- 
cured for less than a dollar per pound. 

AMMONIUM. 

583. Ammonium is a compound of ni- 

What is said _ .... , 

of ammoni- trogen and hydrogen, which is presumed 
**** to be a metal. Its molecule contains one 

atom of nitrogen, to four of hydrogen. If a metal, it 
differs from all others, in being a compound, and not a 
simple element. There are, however, good grounds 

* If sodium is wrapped in paper, to prevent waste of heat, it buriii 
with flame, like potassium, upon water. 



B36 METALS. 

for believing in the existence of such a compound 
gaseous metal. The chloride of ammonium is named 
in accordance with this view. Judging from the prop- 
erties of the salt, we might reasonably expect, by re- 
moval of its chlorine, to obtain from it a substance 
with metallic properties, as well as from chloride of 
sodium or common salt. But the experiment does not 
justify the expectation. As soon as the chlorine is re- 
moved, the metal also decomposes, and a mixture of 
gases is the result. The principal ground for attribu- 
ting a metallic character to the combination of nitrogen 
and hydrogen gases, in the preparations above stated, 
has been already indicated. They supply, in certain 
salts, the place which known metals fill in the other 
and similar compounds. A confirmatory experiment 
is described in the succeeding paragraphs. 

584. Ammonium amalgam. — Another 

State another „ ... , . r 

reason for be- ground for believing in the existence 01 
fxhZiteof'a ammonium with true metallic properties, 
metal ammo- i s found in the following experiment : If 
chloride of ammonium is mixed with an 
amalgam of sodium and mercury, a double ^Sgg&jj 
decomposition ensues. The chlorine and 
sodium unite to form common salt, while the 
mercury combines with the ammonium with- 
out losing its metallic lustre. But there is no 
instance of this retention of metallic properties in the 
combination of mercury or any other metal with any 
non-metallic substance. The inference is that ammo- 
nium is a metal. But any attempt to isolate it by re- 




BARIUM. 



237 



moval of the mercury from the amalgam is ineffectual. 

As soon as this is done the ammonium is resolved into 

gaseous ammonia and hydrogen. This change takes 

place, indeed, spontaneously. 

585. In performing the above experiment, 
How u the \ . „ & . r 

amalgam ex- a small globule of potassium or sodium is 

folmedl pe7 " heated with a thimble ful1 of mercury in a 
test-tube, and a strong solution of sal am- 
moniac added. The mercury increases in bulk without 
losing its lustre, and continues to expand till it fills the 
tube or glass with a light pasty amalgam. 

CLASS SECOND. 

BARIUM—STRONTIUM— CALCIUM— MAGNESIUM. 

586. Barium. — Barium is a soft silvery 
scHption, pro- meta l? easily tarnished in the air. It is 
dnetion and ma de from baryta, by the process already 

solvents * 

described in the section on Potassium. 
Its compounds, including baryta, from which it is pre- 
pared, are hereafter described. Barium is soluble in 
water and most acids. 

587. Strontium. — Strontium is very 
description, similar to barium, but darker in color. . It is 
production produced from strontia by a similar process. 

and solvents? r j r 

Its solvents are also the same. 

588. Calcium. — The metal calcium is 
scription, pro- similar to barium, and is made from lime 
fjvenU? Ud ky the use of potassium, as before de- 
scribed. Its solvents are the same as those 

of the metals above-named. 



238 METALS. 

Magnesium- 589 ' Magnesium.— Magnesium is a soft 
description, white metal, prepared from its chloride 

preparation, . -it • 

solvents and instead ot the oxide, by similar means. 

occurrence? N(me of the metalg of this clasg haye ag yet 

been applied to any useful purpose in the arts. Water 
oxidizes magnesium as it does the other metals of the 
class, but converts it into an insoluble white powder. 
Most acids dissolve it. 



CLASS THIED. 

ALUMINIUM 

590. Description. — Aluminium is a 
bluish white metal made from common 



Aluminium — 
description oc- 
currence, and c i a y # i t j s about one-third as heavy as 
solvents i J 

iron. It fuses at the same temperature 
as silver, and preserves an untarnished surface in the 
air. It does not decompose water, even with the aid 
of boiling heat. Alloyed with iron, it protects the 
latter from the action of the air. This metal is a con- 
stituent of common day, and therefore a part of all fer- 
tile soils and the rocks that produce them. It is also 
a constituent of numerous minerals. By its discovery 
every clay bank is converted into a mine of valuable 
metal. 

Hoio is it pre- 591. Preparation. — Aluminium is pre- 
pared/ pared like magnesium, from its chloride, 
by fusion with potassium or sodium. The latter metal 
is commonly employed. The fluoride may also be 
used in the process, or the mineral cryolite, which 



MANGANESE. 239 

is a compound of fluoride of aluminium with fluoride of 
potassium. The latter constituent interferes in no wise 
with the process. The method of preparing the chlo- 
ride, as a material for the production of the metal, is 
given in the section on Chlorides. 

592. Action of Acids. — Muriatic acid 

Wliat is the . . . . 

action of adds is its proper solvent, and forms with it a 
colorless solution. Nitric acid whitens it, 
if previously dipped into strong potash or soda. Dilute 
sulphuric acid is without action. Aluminium may be 
poured from one vessel to another in a fused condition 
without oxidation. Like silver it may be deposited by 
the galvanic process. 

593. It is highly sonorous, and therefore 

Mention its _ . 

other proper- adapted to manufacture of bells. This 
tus - metal is now prepared in France at about 

ten dollars per pound. The French government propose 
to use it for helmets and cuirasses, for which it is espe- 
cially fitted by its lightness and tenacity. 

594. Manganese. — Manganese is a 

Manganese — . . 

description, grey brittle metal, produced from its oxide 
production, b heating with charcoal. It is found in 

occurrence, J ° 

solvents and nature as black oxide of manganese and as 

uses ? 

a constituent of many other minerals. It 
enters also in small proportions into the composition of 
soils. Diluted sulphuric or muriatic acid are its proper 
solvents, forming with it pale rose-colored solutions. 
The black oxide serves as a source of oxygen, and is 
also employed in the preparation of chlorine gas. It is 
also used in the production of artificial amethysts, and 
also to impart to glass the same violet tint. 

11 



240 



METALS. 



IRON. 




595. Description. — Pure iron is nearly 

Mention some . . 

properties of white, quite soft, exceedingly malleable 
and highly tenacious. It may be rolled 
into leaves so thin that a bound book containing forty- 
four such leaves shall be only one-fifteenth part of an 
inch in thicknesss. In the condition of perfect purity 
it is never seen except in the chemist's laboratory. 
Even the purest iron of commerce contains traces 
of other substances. Dilute sulphuric or 
muriatic acids are its proper solvents, form- 
ing with it green solutions. The addition 
of nitric acid or chlorine changes the color 
to red. Iron may be readily burned, as has al- 
ready been shown in the section on Oxygen. 

596. Occurrence. — Iron is a most 
abundant metal, but is rarely or never 
found in the metallic form, excepting as 
meteoric iron. In this condition it is always alloyed 
with nickel. The latter metal being uniformly com- 
bined with it in masses known to have fallen to the 
earth as meteors, its presence in similar masses dis- 
covered on the surface of the earth, is regarded as evi- 
dence of their meteoric origin. Iron is a constituent 
of a great variety of minerals, of all soils and plants, 
and even of the blood of animals. The peroxide of 
iron, the magnetic oxide, and clay iron stone, are its 
principal ores. Whole mountains of the magnetic oxide 
exist in Missouri and in Sweden. 



Does metallic 
iron occur in 
nature ? 



IRON. 



241 



How is iron 
produced? 



597. Production. — Iron is produced 
from its ores, which are impure oxides, by 

heating with lime, to remove 
the imparity ; and at the 
same time with coal, and 
the gises proceeding from it, 
to remove the oxygen. A 
smelting furnace, such as is 
represented in the figure, 
being previously heated, is 
charged with the material in 
layers, and the heat main- 
tained by the coal of the 
mixture. In the upper part 
of the furnace the materials 
are thoroughly dried. As 
they gradually settle, they 

become more thoroughly heated, and meet carbonic 
oxide from the coal below, which robs the iron of its 
oxygen, and converts it into particles of metal. Still 
lower down, the lime combines with the earthy por- 
tions of the ore, forming a liquid glass. The re- 
duced iron thus liberated, collects, fuses, and sinks to 
the bottom of the furnace. From this point it is run 
off into channels of sand, where it hardens into pig 
iron. 

598. Explanation. — The ordinary im- 
purities of the ore are clay and quartz or 
silica. Lime has the property of forming, 
with both of these, a fusible glass or slag, 

which floats upon the melted iron. This material is 

11 




How is the 
flag formed ? 
For uhat uses 
may it be em- 
ployed ? 



242 



METALS. 



Give the com 
position and 
I roperties of 

cast iron. 



of a light green color. Bat it may be otherwise col- 
ored to suit the taste, and cast into slabs, columns, ar- 
chitectural and parlor ornaments of great beauty. 
The process by which its brittleness is removed, and 
the slag adapted to the above uses, has not been made 
public. 

599. Oast iron — The pig or cast iron, 
as it is called, which is thus obtained from 
the furnace, is not pure iron, but a com- 
pound of iron with carbon. It has ob- 
tained four or five per cent, of this element from the 
coal with which it was reduced. The addition of 
carbon to its composition causes iron to melt more 
readily. But for its absorption, the metal would not 
have become sufficiently soft to flow from the fur- 
nace. Carbon has also the opposite property of mak- 
ing iron harder and more brittle when cold. Castings 
of agricultural implements and other objects, are made 
by remelting the pig iron, and pouring it into moulds 
of the required shape. 

600. Wrought iron. — Wrought iron is 
made from cast iron, by burning out its 
carbon. This is done in what is called a 

reverberatory furnace, such |Tj| 
as is represented in the fig- 
ure. The carbon is burned 
out by the surplus air of the 
flame, which is made to play 
upon the molten iron. From 
the constant stirring which is essential, such a furnace 
for refining iion is called a puddling furnace. The 



How is 
wrought iron 
made ? 




IRON. 



243 



metal becomes stiffer as it loses carbon, and is then 
hammered and rolled into bars. 

601. Iron wire.— The bar or wrought 
^tlTanT iron thus produced, is highly malleable and 
vroperty of d uc tile, and may be rolled into sheets, or 

wrought iron. . XT . . -. 

How is iron drawn into the finest wire. YV ire is made 
wire made? by drawing a wr0 ught iron bar, by ma- 
chinery, through a hole of less than its own diameter, 
and repeating the process until the required degree of 
fineness is attained. Wrought iron loses its tenacity, 
and becomes granular and brittle, like cast iron, by long 
jarring. This effect sometimes occurs in the wheels 
and axles of railway carriages, and is the occasion of 
serious accidents. 

602. Welding. — Wrought iron becomes 
*™4ltiron soft at a certain heat, without melting. 
welded? rp h j s p r0 perty, which adds greatly to its 
usefulness, belongs to no other metal excepting plati- 
num. In the soft state, two pieces may be united by 
hammering. This process is called welding. The 
surfaces to be welded are sprinkled with borax, to pro- 
tect them from the air, which would form a crust of 
oxide of iron and prevent a perfect contact. Its fur- 
ther action is explained in the chapter on Salts. Beside 
borax, other materials having a similar effect are fre- 
quently employed. 

rr . , ' . 603. Steel. — Steel may be made from 

How is steel v J 

made? cas t iron by burning out half its carbon. 

Or it may be made from wrought iron, by return- 
ing half of the carbon which was removed in its 
preparation. The latter is the process generally pur- 



244 METALS, 

sued. It consists in burying the wrought metal hi 
iron boxes containing charcoal, and heating it for 
several days, till combination with a certain portion 
of the carbon is effected. 

604. Annealing. — The hardness of 

How is steel 

made soft or steel depends upon the rate at which it is 
cooled. By heating it to redness, and 
cooling it slowly, it is rendered as soft and malleable as 
wrought iron. This process is called annealing. By 
cooling it very suddenly, it becomes as hard and brittle 
as cast iron. Steel instruments are commonly ham- 
mered out of the soft steel, and subsequently hardened. 
How is steel 605. Tempering steel. — Steel hardened 

tempered? as a "b ve described is too hard and brittle 
for most uses. Any portion of its original softness and 
tenacity may be returned to it, by reheating and slow 
cooling. To restore the whole, a red heat would be 
required. To give back part, and make a steel so 
tough as not to break readily, yet sufficiently hard for 
cutting, a lower temperature is' employed. This process 
is called tempering. The sort of temper imparted de- 
pends upon the degree of heat which has been em- 
ployed. 

606. The proper temperature is ascertained 

How is the i \ . i , 

proper heat by the color which the steel assumes when 
ascertained? heated- Too i s for cutting metal are heated 

till they become a pale yellow ; planes and knives, to 
a darker yellow ; chisels and hatchets, to a purplish 
yellow ; springs, till they become purple, or blue. In 
each case they are afterward slowly cooled. These 
colors are owing to a film of oxide of iron, which is 



CHROMIUM. 



245 



formed upon the steel under the influence of heat. The 
tint is different, according to the thickness of the 
film. All these colors may be seen by heating a knit- 
ting-needle in the flame of a spirit lamp. Where it is 
hottest it becomes blue, and this color shades off into 
pale yellow on either side, like the colors of the solar 
spertrum. 

CHROMIUM. 
607. Description. — Chromium is a grey 

Chroiniicm— . , \ 

description, metal, not readily tarnished and so hard 

oref U solvmts aS t0 scratch g lass - It: is of R0 use in the 

and uses? arts in the metallic form. It is found in 

combination with iron, as chromic iron, and also in 
beautiful crystals, as red chromate of lead. It may be 
prepared from its oxide, like iron, by heating with 
charcoal. Its compounds are much used as paints. 
Chrome green and chrome yellow are among the 
number. Its proper solvents are the same as those of 
iron. The solutions of this metal are green. 

COBALT 



608. Description. — Cobalt is another 
grey metal, tarnishing but slightly in the 
air. It is somewhat malleable. It is found 
combined with arsenic, as arsenical cobalt, 
and in some other minerals. As metal, 
it is without useful application in the arts. It may 
be produced like iron, by heating with charcoal, 



Cobalt— de- 
scription, pro- 
duction, oc- 
currence, sol- 
vents, and 
uses ? 



24b METALS. 

but is more readily reduced by hydrogen. A cur- 
rent of this gas being made to pass through a hot 
tube containing the oxide, it combines with oxygen, 
and passes off with it as water, leaving the metal in the 
form of a fine powder. Its proper solvents are the 
same as those of iron and chromium. The solutions 
of cobalt are pink. The oxide is employed for im- 
parting a blue color to glass. 

NICKEL. 

Nickel— 609. Nickel is still another grey metal, 

prediction lighter in color and more malleable than 
ores, solvents, cobalt, and not much affected by the air. 

and uses? , n . . 

It is found m combination with copper, in 
the mineral called copper nickel. It may be prepared 
by either of the methods used for cobalt. Its proper sol- 
vents are the same as those of the last four metals. The 
solutions of this metal are green. Nickel is principally 
used in the preparation of the alloy called German sil- 
ver. This imitation of silver is brass rendered white 
by the proportion of nickel which it contains. The 
alloy is composed of one hundred parts of copper, six- 
ty of zinc, and forty of nickel. 



ZINC. 
610. Description. — Zinc is a bluish- 

Zinc — de- 
scription white metal readily tarnished in the air. 

°veni%T d *° 1 ' It; is brittle at ordinary temperatures, and 
converted into vapor at a red heat. If 




zinc. 247 

heated somewhat above the temperature of boiling wa- 
ter, it can be rolled into sheets. At a higher tempera- 
ture it again becomes brittle. Sulphuric and muriatic 
acids dissolve it readily, forming colorless solutions. 
It is not found native. The red oxide, and the carbon- 
ate, called calamine, are among its more important ores. 

611. Production. — Z.nc is produced 

How is zinc . • ■■■■•■« • i * i 

produced? trom its oxide by heating with charcoal to 
^toitu*ed* y remove the oxygen, or, in other words, to 
reduce it. When made from the carbonate, 
the ore is previously roasted, to expel 
its carbonic acid and bring it to the 
state of oxide. As the metal is volatile 
at the heat required in its reduction, an 
ordinary furnace, such as is used for making iron, can- 
not be employed in the process : the metal would be 
lost in vapor. A clay retort or muffle, such as is re- 
presented in the figure, is used instead. The zinc va- 
por condenses in the cool neck, and falls in drops of 
melted metal into a vessel of water placed to receive 
it. The carbonic oxide produced in the process at the 
same time, escapes into the air. It will be observed, 
that the process is essentially the same as that for pro- 
ducing potassium and phosphorus, as before described. 
Acids dissolve zinc, forming colorless solutions. 

612. Action of heat and air. — Zinc 

How may zinc 

be bumed? may be burned by heating it on charcoal 

Row melted? ^ ^ Wow . pipe flame> It ^^ ^ CQn _ 

verts itself rapidly in the process into 
white oxide of zinc. If an intense 
heat is employed, the vapors of the 
metal burst through the crust and bum 




248 METALS. 

to oxide, with a brilliant greenish flame. When ^mc 
is burned in considerable quantity in a highly heated 
crucible, the oxide forms flakes in the air, to which the 
name of lana philosophica or philosophers' wool, was 
given by the alchemists. The metal may be melted 
over a spirit lamp, in an iron spoon. 
Mention the 613. Uses of zinc.— Zinc is principal- 

uses of zinc. \y employed in the form of sheet zinc, for 
roofing and similar purposes. It is also used, like tin, 
as a coating to protect iron chains and other objects 
from rust. The coating is effected by plunging the 
iron into molten zinc, which forms an alloy upon its 
surface. The iron thus coated is sometimes called gal- 
vanized iron, though without reason, as is evident from 
the above process. Solutions of zinc are sometimes 
used to prevent the decay of wood, and to render it 
less combustible. It has also been employed with 
success, as a substitute for copper, in sheathing vessels. 



CLASS FOURTH. 

TIN. 
614. Description. — Tin is a brilliant 

ijcscrihe the 

metal Tin. white metal, very soft and malleable, and 
From what not eas ily tarnished. When a bar of tin 

ore is it made ? J 

is bent, it gives a peculiar grating sound, 
fancifully called the cry of tin. This is a consequence 
of the friction of the minute crystals of tin of which 
it is composed. Its only ore is an oxide, called tin 



tin. 249 

stone, of which Cornwall, England, is the principal 
locality. 

How is tin 615. Production. — Tin is produced, 

produced * like iron and most other metals, by heating 
its oxide with carbon. The materials are heated in a 
small blast furnace. The carbonic oxide produced in 
the fire, as before explained, is the reducing agent. It 
takes the oxygen from the ore, and passes off with it 
as carbonic acid, while the metal fuses and runs to the 
bottom of the furnace. By heating tin before the 
blow-pipe, it is rapidly converted into white oxide. 
How do adds 616. Action of acids. — Tin resists 

act on tin I weak acids remarkably. Dilute muria- 
tic and sulphuric acids, which dissolve most of the 
metals before described, act upon it but feebly. The 
concentrated acids dissolve it with comparative ease. 
Its solution, although less poisonous than those of 
lead, are still injurious to health. Acid food should, 
therefore, never be allowed to stand for a long time in 
tin vessels. The solutions of tin are colorless. 

617. Nitric acid acts upon tin with en- 

What is the , 

action of ni- ergy ; but, like a ferocious animal that de- 
stroys without devouring its prey, leaves 
it undissolved. It converts it into a white 
insoluble powder of oxide of tin, with the 
evolution of the usual red fumes. This case 
is an exception to the usual action of nitric 
acid. One portion of the acid commonly 
acts to produce oxide, while another portion dissolves 
the oxide formed. The experiment for the solution 
11* 




250 METALS. 

of tin may be made vith tin-foil, in a tea-cup or test- 
tube. 

618. Aqua-recria, it will be remembered, 

What is the . . * _ ° . \ . . . ' 

action of aqua- is a mixture of nitric and muriatic acids. 
regia on tin . j n most cases they act, as before described, 
in concert, to dissolve metals that neither can dissolve 
alone. They act thus, also, upon tin, in small por- 
tions. But if larger quantities are employed, the mix- 
ture grows warm, and- the nitric acid, as if stimulated 
beyond restraint, attacks the metal for itself, and con- 
verts it, as when it acts alone, into a white powder. 

619. Coating pins. — Common brass pins 

How are pins _ M « • i e 

coated with are coated, by boiling with cream of tartar 
and tin-foil or bits of tin. The acid of 
the tartar acts as solvent. Tin is then deposited on 
the mere electro-positive brass, as in cases of galvanic 
decomposition. At every point where brass, tin, and 
the liquid are in contact, a small galvanic battery is in 
fact produced. 

How is tin 620. Tin ware. — Tin is cast in va- 

plate made ? r i us forms, for culinary and chemical uten- 
sils. A little lead is added to give it greater tough- 
ness. Common tin ware is made of sheet-iron coated 
with tin. The coating of the metal is effected by 
dipping well cleaned sheet-iron into molten tin. 

621. Crystalline tin. — Tin has a great 

How may the n . , . „ 

crystalline tendency to assume a crystalline form. 
structure of rpj^ s t mc ture may be observed on wash- 

hn be seen ? J 

ing the surface of ordinary tin plate with 
aqua-regia, to remove the thin coating of oxide. It 
may be still better seen if a tin plate is heated over a 



ANTIMONY. 251 

lamp till the coating melts, then suddenly coolea and 
afterward cleaned as above directed. The whole sur 
face is then found to be covered with beautiful cry* 
talline forms. 



ANTIMONY. 

Describe the 622. Description. — Antimony is a blu 

T^ al From°' ish white and hi § hl y crystalline metal 
what ore is it which does not tarnish in the air. It is 

obtained? . . , . _ _._ _ 

so brittle that it may be readily reduced to 
powder. The ore from which the metal is produced is 
the grey sulphuret, or antimony glance. 

623. Production. — Antimony may be 

How is anti- . . . 

mony pro- obtained from its oxide by the usual pro- 
cess of reduction. The sulphuret is first 
partially converted into oxide by roasting, and still fur- 
ther by carbonate of soda, which is added in the sub- 
sequent process. It is then mixed with charcoal, and 
intensely heated in crucibles. At a white heat the 
metal fuses and sinks to the bottom. The soda added 
in the process exchanges its oxygen for the remaining 
sulphur of the ore. 

624. Action of heat and air. — If heated 

How may an- ,-,,,. 

timony be before the blow-pipe, antimony soon melts, 
and burns with a white flame. It is at the 
same time converted into oxide. A portion of the oxide 
escapes into the air, while the rest forms 
a white coating upon the charcoal sup- 
port. At the high temperature which ' 
js here produced, the affinity of the 




252 METALS. 

metal for oxygen is so stimulated, that the molten 
globule will continue to burn, even if removed from 
the flame. By directing a stream of air upon it, 
from a pipe-stem, the combustion may be maintained 
till the globule is entirely consumed. 

625. If the molten globule is allowed 

Describe an r ,. in • 

experiment to fall upon the floor, it 1m- ■ ; . 
with the mol- me diately divides into hun- \\\ |/'v. 

ten globule f J •< S N \\ \i/s~'\ m 

dreds of smaller globules which - 



;'/ »\ns 



radiate in all directions, leaving each a dis- '/VV«\\^ 
tinct track of white oxide behind it. 

What is the 626. ACTION OF CHLORINE. A shower 

£°lf:S- of fire ma Y be produced by sprinkling fine 
mony ? powder of antimony into a vial containing 

chlorine gas. The metal is hereby converted into a 
white smoke of chloride of antimony. In its rela- 
tions to the principal acids, antimony resembles tin. 
Its solutions are colorless. 

What are the 627 ' Us*S OF ANTIMONY.— The principal 

principal uses use of antimony is in the preparation of 
of anti lojii/ . a ]j y Sj t0 kg hereafter described. Among 
these, type metal is the most important. Many of the 
compounds of antimony, like other poisonous sub- 
stances, are used with advantage in medicine. Tartar 
emetic is one of these medicinal compounds contain- 
ing antimony. 




BISMUTH. 253 

CLASS FIFTH. 

BISMUTH. 

m*ni*th-de- 628 - Description.— Bismuth is a brittle, 
scription, sol- crystalline metal of a reddish white coloi. 

vents, and oc- . . 

curreuce in It is used in making certain alloys. Like 
antimony it can be readily ground to pow- 
der. Crystals of bismuth may be obtained by 
the method described in the section on Sulphur, 
as represented in the figure. Nitric acid is its 
proper solvent and forms with it a colorless solution. 
Bismuth is found native, forming threads of metal in 
quartz rock. Its most productive localities are in 
S axony. 

629. Production. — The metal is pro- 

How is uis- ii-i • 

muthprodti- cured from the rock which contains it, by 
simple heating in inclined tubes. At a 
comparatively moderate temperature the bismuth fuses 
and runs down into vessels placed to receive it. 
^ 630. Effect of heat and air. — The 

What is its 

action before same experiments before the blow-pipe, 
the blow-pipe? and wkh molten globules, which were 

described in the case of antimony, 
may be made with bismuth. The 
only difference is, that the metal does 
not burn with flame, and that the coat- 
ing of oxide on the charcoal is yellow, instead of white. 
631. Uses of bismuth. — Its principal 

What are the . 

uses of bis- use is in the prepaiation of alloys, to be 
described hereafter. One of them has the 




254 



METALS. 



remarkable property of fusing in boiling water. Seve- 
ral compounds of bismuth are used in medicine ; the 
sub-nitrate, is also employed as a cosmetic. This 
use of it is quite hazardous, as certain gases which are 
often present in the air, have the effect, as will be here- 
after seen, of changing its color to a deep brown or black. 



Copper — de- 
scription, 
ores, solvents? 



COPPER. 

632. Description. — Copper is a red, 
malleable, and highly tenacious metal. It 
tarnishes in the air, but is less injured by 

rust than iron, and therefore more durable. Nitric acid 
is its proper solvent, and forms with it a green solution. 
Copper is found in abundance, in the metallic condi- 
tion, on the southern shore of Lake Superior. It is 
chiseled out, in masses, from the rocks which contain 
it. The metal is more commonly obtained from a 
mineral called copper pyrites, which is a double sul- 
phuret of iron and copper. It is also found as pure 
sulphuret, red oxide, and carbonate. Minute traces of 
copper are found in human blood. 

633. Production. — Copper is prepared 

State briefly „ , 

the mode of from the impure 

production. su i p huret, by 

first burning out the sulphur 

in the air; and secondly, 

heating with charcoal to 

remove the oxygen which 

has taken its place. Sand 

is at the same time added, to form a floating slag with 

the oxide of iron, and thus remove it from the molten 

copper. 




copper. 255 

The oxide of iron Jius removed, is derived from the 
sulphuret of iron which is a usual constituent of cop- 
per ores. 

State further ^ B ° th ° f the ab ° Ve Presses of 

particulars of roasting and heating with charcoal and 
epro sand, must be several times repeated 

before pure metallic copper is obtained. It is to be 
remarked that the formation of a slag which shall 
remove this iron, depends on the fact that its oxide is 
by no means so easily reduced as copper. Being once 
brought into the state of oxide, it remains in this con- 
dition and unites with the silicic acid of the sand. 
1JTJ . ., 635. Action of heat and air. — At a 

w /tat zs trie 

effect of heat high temperature, copper is readily oxi- 
andair? dized in the air. Its oxidation may be ob- 

served by holding a copper coin in the flame of a spirit 
lamp, as described in the section on Flame. The iri- 
descent hues observed in the experiment, are owing to 
the varying depth of oxide on different portions of 
the coin. By long continuation of the process, the 
whole surface is converted into black oxide. If it is 
sooner suspended, and the coin plunged into cold 
water, a coating of red oxide containing less oxvgen 
is obtained. 

636. Uses of copper. — Copper is used 

Mention some . /»!•*■ 

of the uses of for a variety of purposes for which iron 
copper. would be less suitable on account of its 

rapid oxidation. Its employment in sheathing ships, is 
an example. It is also a constituent of various alloys, 
to be hereafter described. Among these, all gold and 
silver coins, and the metal of gold and silver pta*e are 
included. 



256 



METALS. 



LEAD. 



, _ , 637. Description. — Lead is a bluish 

Lead — de- 
scription, ores grey metal, extremely malleable, and read- 
and solvents? fly tarnished in the air# It is heavier than 

any other of the metals mentioned in this work except 
mercury, gold, and platinum. Nitric acid is its proper 
solvent, forming with it a colorless solution. The 
principal ore of this metal is gahna or sulphuret of 
lead. Lead is also found as carbonate, sulphate, and 
phosphate of lead. 

How is lead 638. Production. — Lead is obtained 

obtained? from the sulphuret by heating it with 

iron, to remove the sulphur. A mixture of metallic 
lead and sulphuret of iron are 
thus produced, from which 
the lead separates by its 
greater specific gravity. If 
the oxide of lead could be 
readily obtained, the reduc- 
tion by charcoal would be 
as applicable here as in the case of other metals. 
Explain an- 639. A second method. — Another 

other method. me t,hod, is to heat the sulphuret with a 
portion of sulphate. The sulphate has a large supply 
of oxygen, while the sulphuret is destitute of this ele- 
ment. The two may be mixed in such proportions 
that they will together contain just enough oxygen to 
carry off all the sulphur as sulphurous acid. This 
result having been accomplished by heat, the pure 
metal of both remains behind. As a preparation for 





LEAD. 257 

this process, a portion of sulphuret is converted into 
sulphate by heating in a reverbaratory furnace. Both 
parts of the process are in practice united ; a moderate 
heat with abundant air being first supplied, a portion 
of sulphate is produced. This is afterwards more 
highly heated, with the undecomposed sulphuiet which 
remains. 

640. Action of air and heat. — If 
when lead is l ea d is heated before the blow-pipe in the 
heated before oxidizing flame, it melts and disappears. 

the blowpipe ? - ° ' * r 

The charcoal support becomes at the same 
time covered with yellow oxide of 
lead or litharge. The grey coating 
which at first forms upon the lead, is 
an oxide containing less oxygen. If, 
on the other hand, litharge is heated in the reducing 
flame, it is converted into metal. 

641. Action of Water. — Water, with 

What i* the . .... . 

action of water the help ol the air which it always con- 
on lead. tains, acts sensibly upon lead and becomes 

in consequence poisonous. This action of water is 
most decided when it contains no foreign matter. On 
being conducted through leaden pipes, it becomes 
therefore more impure as a consequence of its very 
purity. 

\Yhat prevents 642. The presence of sulphates andcer- 
this action? tain other salts, such as are usually con- 
tained in spring water, prevents this effect. Those sub- 
stances whose presence in water we are accustomed 
Lu regret as impurities, thus become our most efficient 
protectors against the poisonous effects of lead. 



258 METALS. 

643. But this rule is not without ex- 

Do imparities . . 

always pro- ception. Certain substances seem to in- 
crease the action. It is therefore always 
prudent where it is proposed to conduct water through 
leaden pipes, to ascertain by direct experiment, whether 
the particular water in question acts upon the lead or 
not. 

644. Illustration. — The difference in 

Describe the . 

experiment the action of pure water upon lead, and 
with lead and ^^t which contains foreign substances in 

distilled water. ° 

solution, may be readily proved by exper- 
iment. For this purpose, bright slips of lead may be 
placed in two tumblers, the one containing rain water, 
and the other well or spring water. The former will 
soon become turbid while the latter remains unaffected. 
64o. The presence of lead in the former 

How may the 

presence of case may be still more strikingly shown, 
U shown) hettCr h y adding to the water a few drops of a 
solution of hydrosulpluric acid. The for- 
mation of a dark cloud will show the presence of lead 
and indicate the danger to be apprehended. 

646. Lead Tree. — Dissolve some crys- 

D escribe the 

had tree and tals of sugar of lead in thirty or forty 

the reason of t j their b Jfc f t d fiH a v i a l 

its production. 7 

with the solution. A strip of zinc hung 
in the vial will branch out in a beautiful ar- 
borescence of metallic lead. It may be neces- 
sary to clarify the solution by the addition of 
a little clear vinegar or acetic acid. A day or 
two will be required for the completion of 
the experiment. The effect depends on the 




MERCURY. 259 

superior affinities of zinc for acetic acid. The zinc 
takes away acid and oxygen from successive portions 
of the sugar of lead, and leaves the particles of lead 
subject to the laws of crystallization. At the same 
time, the zinc having acquired possession of the acid 
and oxygen comes into solution as acetate of zinc. A 
similar arborescence is produced in a solution of silver 
by metallic mercury. 

How are shot 647. MANUFACTURE OF SHOT. Shot are 

made? prepared by pouring melted lead through 

perforated iron vessels. The drops are made to fall 
from a great height, that they may become cooled and 
solidified in their descent. They are caught in water 
that their shape may not be impaired. Having been 
assorted by means of seives, they are polished in 
revolving casks containing a small portion of black lead 
or plumbago. 

Mention other ^48. OTHER USES OF LEAD. — In the 

uses of lead. form of sheet lead this metal is applied 
to a variety of familiar uses. It is also largely em- 
ployed in the manufacture of lead tubing. It is a 
constituent of various alloys, among which pewter 
and type metal are the more important. 

CLASS SIXTH. 

MERCURY. 
649. Description. — Mercury is'a white 

^fercurv de~ 

scription, sol- fluid metal of high lustre and beauty. It 
vents, ores retains the fluid condition at all ordinary 

discovery ? J 

temperatures.and is only rendered solid by 



260 METALS. 

extreme cold. Nitric acid is its proper solvent. Mer- 
cury is sometimes found in the metallic form, but more 
commonly as the sulphuret or cinnabar, which is its 
principal ore. It is said that the mines in Mexico were 
accidentally discovered by a native hunting among the 
mountains. Laying hold of a shrub to assist him in 
his ascent, he tore it up by the roots, and a stream of 
what he supposed to be liquid silver flowed from the 
broken ground. 

Howismer- 650. Production. — Mercury is prepared 

cury obtained? f rom the sulphuret, by simple roasting in a 
current of heated air. This metal yields its sulphur so 
readily to the oxygen of the air that no other agent is 
essential in its production. The mercurial vapors pass 
along with the gas, into tubes or chambers where the 
temperature is lower, and are there condensed to the 
liquid form. 

Mention other 651. Mercury may also be produced from 
methods. fae sulphuret by the employment of iron 

filings to remove the sulphur, as in the case of lead. 
Burned lime may also bis used. Its calcium combines 
with the sulphur and uses its own oxygen for the 
partial conversion of the sulphuret thus formed into 
sulphate of lime. 

. , 652. Action of heat and air. — Mercury, 

What is the J1 

action of heat like water, may be boiled away and con- 
ZltwryT verted into vapor by the application of 
heat. At 39° below zero it freezes. It is 
always to be borne in mind in experiments with this 
metal and its compounds, that its fumes as well as its 
salts are extremely poisonous. By free access of air and 



MERCURY. 261 

moderate heat, mercury may be gradually converted into 
red oxide, but a higher temperature expels the oxygen 
thus absorbed, and the oxide is again converted into 
metal. This production of a metal from an oxide, by 
heat alone, is characteristic of the noble metals. They 
are loth to obscure their splendor in rust ; if it is forced 
upon them, they need but little assistance of heat to 
throw it off and re-assume their original beauty. 

653. Amalgams — Glass Mirrors. — 

\V7tat are 

amalgams? Mercury combines with many metals form- 
rors 'silvered? * n § com P oun ds which are called amalgams. 
When the mercury is in large proportion 
they are fluid. Gold, silver, and lead, for example, 
may be dissolved in mercury. This solvent power of 
mercury is usefully applied in extracting gold from the 
rocks which contain it. The beautiful silvering of 
mirrors consist of an alloy of tin and mercury. Tin 
foil is applied to the glass, and being afterward drenched 
with mercury, the excess is removed by pressure. The 
tin has thus absorbed about one-fourth of its own 
weight of mercury. 

654. A copper coin may be similarly 

How may a 

copper coin be silvered by rubbing with metallic mer- 
veredT y ** cury, or keeping it well moistened for some 
time with a solution of mercury in nitric 
acid. If the solution is quite acid, it must first be 
nearly neutralized by ammonia. The coin is to be af- 
terward polished. The chemical action which takes 
place in this case is similar to that explained in the 
case of the lead tree. By drawing a line across a thin 
brass plate with a pen dipped in solution of mercury, 



262 METALS. 

the plate will be so weakened that it may afterward 
be readily broken. 

655. Other uses of mercury. — The 
Mention some compounds of mercury are extensively 

other itses of * a J * 

mercury. used in medicine. Corrosive sublimate, a 

poisonous chloride of mercury, is employed 
for the destruction of vermin. It is also used in what 
is called the kyanizing process, to impregnate wood 
and other vegetable and animal substance, and thus 
prevent their decay. Another important use of mer- 
cury is found in the manufacture of barometers and 
thermometers. It is especially adapted to the measure- 
ment of heat, by its fluidity at low temperatures and 
its ready and equable expansion. 



SILVER. 
656. Description. — Silver is a lustrous 

Silver ~~~de~ 

scription, ores white metal of perfect ductility and malle- 
ar solvents? dbilitjr> Its loss of ]astre on exposure, is 

owing to the presence of a small proportion of sulphur- 
etted hydrogen in the air. Nitric acid is its proper sol- 
vent, though for certain purposes oil of vitriol is pre- 
ferred. Silver is often found native, but more fre- 
quently combined with sulphur as silver glance. 
Galena or sulphuret of lead always contains it in small 
proportion, and sometimes to the amount of one or 
two per cent. 

Howissilvet 657. Production. — Silver is prepared 

obtained? from the sulphuret, by first roasting the ore 



SILVER. 



263 



with common salt, in order to convert it into chloride. 
Iron is subsequently employed to remove the chlorine 
and isolate the metallic silver. 

Give the com- 658. Mercury is added with the iron, in 
plete process. orc j er t h at j t ma y dissolve the silver from 

the mass of roasted ore and iron as fast as it is formed. 
The materials are agitated with water for many hours 
together. At the end of the process the mercury, with 
its load of silver, is drawn off from the bottom of the 
cask. The solution of silver in mercury is afterward 
filtered through buckskin or closely woven cloth, which 
allows a large part of the liquid metal to pass, while 
the silver with a small portion of mercury is detained. 
The silver is then freed of its remaining mercury by 
heat. The above process is called amalgamation. 

., , 659. Silver obtained from lead. — 

JjescTioe the 

process for Almost all lead, as produced from galena 

leV/Tomlfad. and its other ores > contains a certain pro- 
portion of silver. The latter metal may 
be freed from a large part of the lead by melting the 
alloy and then allowing it to cool slowly. Most of 
the lead solidifies in small crystals, and may be skim- 
med out with an iron cullender. An alloy containing 
silver in large proportion remains in the liquid condi- 
tion. It is afterwards solidified by further cooling. 
The above is called Pattinson's process. 

660. Cupellation.— The remainder of 
How is the re- j ea( j j s separ ated from the silver by con- 

maininq lead r _ 

separated? verting it into oxide, in a current of heated 

air. The silver does not oxidize under 

these circumstances, but retains the metallic form. 

12 



264 



METALS. 



The mass of metal grows smaller as the process pro- 
ceeds, till finally pure silver remains. The moment 
of its production is indicated by a beautiful play of 
colors and a sudden brightening of the metal. The 
above process is carried on upon a hollowed and com- 
pacted mass of bone-ash called a cupel. The object of 
the cupel is not alone to support the metal, but to ab- 
sorb the hot and fused oxide of lead as fast as it is 
formed. If a little copper is present, it is also absorbed 
with the lead. The process is called cupellation. 
_. , 661. It may be illustrated on a small 

How may the 

process beiU scale, by making an excavation in a piece 
ustrate ? Q f q^^qq^i^ anc [ pressing into it a lining 
of well burned and moistened bone 
ash. A globule of lead, to which a little 
silver has been added, is to be heated 
on the support in the oxidizing flame. 
For separating a small quantity of lead from silver, 
the bone ash is not essential. The process may be 
conducted before the blowpipe, upon the naked char- 
coal. A small portion of silver may often be obtained 
from the lead of commerce by this means. 
What is said ^62. Silver coin. — The standard sil- 

of silver coins? yer f t h e United States is an alloy con- 
taining ten per cent, of copper. Silver plate should 
have the same composition. The object of alloying 
with copper, is to impart greater hardness to the metal, 
and secure against the gradual loss from attrition which 
would otherwise occur. Spanish silver often contains 
a small proportion of gold. The gold is left as a black 




SILVER. 



265 



powder, in dissolving such coins in nitric acid. Its 
color and lustre may be brought out by rubbing. 

663. The Silver assay. — Assaying is 

wV/lClt 2 9 CLS~ 

saying, and ^e process by which the proportion of met- 
why necessa- a } s j n an a n y i s ascertained. In all estab- 
lishments where money is coined, assaying 
is an important part of the work of the establishment. 
The precious metals, as received at the mint, commonly 
contain a certain proportion of other metals. But it 
may be too much or too little. It is the business of the 
assayer to ascertain its precise composition, that the 
metal may be rendered purer, if necessary, or be fur- 
ther alloyed if found purer than the standard. 

., T 664. As a preparation for the silver as- 

JJ escribe the x x 

process of as- say, a sample, containing an ounce or other 
saymg. definite weight of the impure metal, is dis- 

solved in nitric acid. The dissolved silver has the pro- 
perty of becoming solid again, and sinking 
to the bottom of the clear solution as a white 
curd, just in proportion as common salt is fur- 
nished to it. But the other metals which 
may be present as impurities have no such 
effect. It follows, that the amount of silver 
present, is just in proportion to the amount of 
salt it is necessary to supply before the pre- 
cipitation or formation of the curd ceases. Now, the 
assayer knows beforehand, how much salt he must 
supply to the solution of an ounce of metal if it be all 
silver. If he finds that an ounce of the sample, re- 
quires to be supplied with the same quantity before the 
precipitation ceases, he knows that the metal is all silver ; 

12 




266 METALS, 

if but half as much is required, he knows that it is 
but half silver. Having ascertained the true proportion, 
the assay is completed. The salt required in the pro- 
cess is employed in the form of a solution, and the 
quantity used is known by pouring it from a graduated 
vessel. 
„ _ . , 665. Explanation. — The curd which 

Explain the 

chemical ac- forms in the above process is insoluble 
alovTprocess. chloride of silver, formed from the silver of 
the solution and the chlorine of the salt. 
The nitric acid and oxygen, which were combined 
with the silver, at the same time unite with the sodium 
forming nitrate of soda which remains in solution. 

666. Silver separated from coppeh. 

J)escfibe the 

method of ex- Copper obtained from certain ores con- 
trading silver ta i us s0 mi ich silver as to make its separa- 

from copper. r 

tion an object of importance. The method 
pursued is to fuse the copper with lead. As the lead 
flows out again by subsequent fusion, it brings with it 
all the silver, and the copper remains behind as a spongy 
mass. This process is called liquation. The silver is 
then freed from lead by the process of cupellation al- 
ready described. 

Mention some 667. IFsES OF SILVER.— Most Uses of 

uses of silver, silver are so familiar that they need not be 
here mentioned. Its employment for daguerreotype 
plates depends on the fact that the color of many of 
its compounds is readily changed by light. This sub- 
ject is more fully considered in the section on Chlo- 
rides. The nitrate of silver or lunar caustic, is used 
in surgical operations, to burn or cauterize the flesh. 



GOLD* 267 

In solution, it is also employed as a hair dye, and in 
the production of indelible ink. 

GOLD. 

Mention some 668. Description. — Gold is a yellow 

P /oZ rH lis°£l. metal of brilliant and permanent lustre. 
vent, and Its extreme malleability is strikingly illus- 
trated by the fact that it may be hammered 
into a leaf but little more than ^olo o o °f an inch in 
thickness. As the fact may be otherwise stated, a cube 
of gold five inches on a side could be so extended as 
to cover more than an acre of ground. Such gold leaf 
is permeable to hydrogen. A jet of this gas may be 
blown through it and kindled on the opposite side. 
Gold is proof against all ordinary acids excepting aqua- 
regia. It is found only in the metallic state, and com- 
monly either in quartz rock or in the sands of rivers. 
Native gold contains from five to fifteen per cent, of 
silver. 

How is pure ^69. PRODUCTION. The REFINING PRO- 

ffoid produced CESS# — Native gold may be freed from the 
silver which it contains, by the agency of concentrated 
sulphuric or nitric acid. A difficulty in accomplishing 
this result arises from the fact that every particle of silver 
is so perfectly surrounded by gold, that the acid does 
not readily reach it. This difficulty is overcome by 
fusing more silver into the gold, and thus opening a 
passage for the solvent. This being done, both the 
original silver and that which has been added are read- 
ily removed. The above is the process at present pur- 
sued in France for refining gold. 



268 METALS. 

Describe an- ^70. ANOTHER METHOD.— The Second 

other method, me thcd is essentially the same as that al 
ready described, with the substitution of nitric for sul 
phuric acid. The addition of silver, as a preliminary 
step, is found necessary in this process also. So much 
silver is added, that the gold forms but a quarter of the 
mass exposed to the action of the acid. The methcd 
is hence called quariation. # The process involves a 
previous knowledge of the approximate composition 
of the mixed metal. This may be obtained by the 
imtc/tsfone, as hereafter described. 

Whatisamal- 671. AMALGAMATION. Gold may be oh- 

gamation? tained from any material which contains 
it j even in small proportion, by the process of amalga- 
mation. This process consists in agitating the finely 
divided material with mercury, until the latter has ex- 
tracted all of the precious metal. It is then obtained 
from its solution in mercury by the same means em- 
ployed in the case of silver. This method is adopted 
in the case of the gold-bearing quartz of California. 
The dust of jewelers shops is similarly treated in order 
to save the small proportions of gold which it contains. 
672. Gold from lead and copper. — 

How is gold . _ 

separated Certain ores oi lead and copper contain so 

from lead and much ]( j that it ig pro fi ta ble to extract it 

copper f ° r 

from the metal which they yield. This 
is done by the processes of liquation and cupellation be- 
fore described. 



* In the practice of the United States Mint, the addition of less 
silver has been found sufficient. The proportion of gold is there 
increased to one-third. Nitric acid is then employed in the refining 



process. 



GOLD. 269 

673. Gold from sulphurets of iron, 
ob°taiued°fro7n & c - — Sulphurets of iron, copper, &c, 
certain ml- sometimes contain gold, in small quantity, 

phurets? u J 7 

and so completely disseminated that it can- 
not be readily extracted by mercury. It has been found 
advantageous to heat such ores with nitrate of soda, 
previous to amalgamation, The sulphurets are thus 
partially converted into sulphates, which can be washed 
out. What remains of the pulverized material is at 
the same time thoroughly opened to the action of mer- 
cury. 

Describe the 674. The GOLD ASSAY. Gold tO be as- 

method of as- sa y e d contains commonly only silver and 

saying gold f ' ■ 

Why is silver copper as impurities. By fusing the sam- 
ple with lead and then removing this 
metal by cupellation, it carries with it the copper, into 
the cupel. A globule containing only gold and silver 
remains. The silver is then dissolved out by nitric 
acid. The remaining sponge of pure gold being 
weighed, and its weight compared with that of the orig- 
inal sample, the assay is completed. More silver is 
added in the process, for reasons stated in a previous 
paragraph. 

What is the $75. ASSAY OF GOLD BY THE TOUCH- 

touchsto?ie stone. — Any hard and somewhat gritty 

and how is it J ° J 

used in assay- stone of a dark color which is not acted 
tn ff 9° < on by acids answers the purpose of a touch- 

st me. The assay consists in marking upon the stone 
with the alloy, and judging of the purity of the metal 
from the color of the mark, and the degree in which 
it is affected by an acid. Nitric acid, to which a very 



270 



METALS. 



small quantity of muriatic acid has been added, is em- 
ployed in this test. Gold alone is proof against its 
action. In proportion to the permanence of the mark, 
is the purity ot the gold which has been submitted to 
the assay. 

What is said 676. Gold Coin. — The gold employed 
of gold coin ? f or co ^ pj ate and j evve i r y i s always alloyed 

with a certain portion of copper or silver, to give it 
greater hardness. The standard gold of the United 
States is nine-tenths pure gold, the remaining tenth 
being an alloy of copper and silver. 

677. Purity of gold. — The purity of 

How is the e?e- . ■ 

gree of purity gold is expressed in carats, a carat signify- 
tres°sc d dV~ in »> practically, one twenty-fourth. Thus, 
when gold is said to be sixteen carats fine, 
it is meant that two-thirds of it is pure gold. Gold 
eighteen carats fine is three-fourths pure gold and one- 
fourth alloy. 

678. Gilding. — Gilding by the galvanic 

How is copper 

jewelry gild- battery has been already described. This 
method is, in most cases, preferable to all 
others. Copper jewelry is thinly gilded by boiling in 
a solution of gold in carbonate of soda or potash. The 
solution is prepared by first dissolving the gold in aqua 
regia, and afterward precipitating and re-dissolving it 
by means of the carbonate above named. 

679. Gilding mav also be effected by an 

Describe the * 

method of gild- amalgam of gold and mercury. The amal- 
% a 9 ai V an S am ^ e ^ n § a ppli e( i, the mercury is expelled 
by heat and the gold remains. This me- 
thod is very frequently employed. A coating of pure 



PLATINUM. 



271 



gold is produced upon articles of jewelry, made of im- 
pure metal, by first heating them, and then dissolving 
out the copper by means of nitric acid. 



PLATINUM. 
680. Description. — Platinum is the 

Platinum — 

Description, last of the noble metals. It resembles 

llfoeZsf' stee * * n c °l° r > aQ d possesses a high degree 
of malleability. It is the heaviest and the 
most infusible of all metals. At a white heat it may 
be welded like iron. Like gold it resists the action 
of any single acid, but may be dissolved in aqua-regia. 
It is commonly found, like gold, in small flattened 
grains in the sand of certain rivers. Its pecuniary 
value is about half that of the more precious metal. 

681. Platinum condenses gases. — The 
metal platinum has the remarkable pro- 
perty of condensing gases upon its surface, 
and thereby increasing their affinities. 

This effect is in proportion to the surface 
exposed. It may be prepared for this experi- 
ment by burning paper, previously moistened 
with a solution of this metal. Such an ash, 
by simple exposure to the air, condenses and 
retains a large quantity of oxygen within it? 
pores. On holding it in a jet of hydrogen, 
the condensed oxygen immediately unites with the 
latter gas so energetically as to inflame it. 

682. Platinum is employed for similar 

Give another 

illustration of purposes, in the form of a sponge, and as a 
this effect powder, called platinum black, A mixture 



Mention a re- 
tnarkable ef- 
fect of plati- 
num on gases. 




272 METALS. 

of nitric oxide and hydrogen, passed through a tube con- 
taining heated platinum black, issues from the tube as 
ammonia and water. The hydrogen has entered into 
combination with both of the elements of the nitric 
oxide, producing two new compounds. 

Why isplati- 683. OTHER USES OF PLATINUM. The 

num superior m ost important use to which platinum is 

to other metals m x x 

for che. kal applied in the arts, is in the manufacture 
apparatus. Q ^ q^q^^ apparatus. Its extreme in- 
fusibility and resistance to acids, adapt it especially to 
this purpose. In the manufacture of oil of vitriol, for 
example, no other material excepting gold could well 
take the place of the platinum vessels in which con- 
centration is effected. Platinum crucibles are also in- 
valuable, as they may be exposed to the fire of a blast 
furnace without injury. Nothing less than the most 
intense heat of the oxyhydrogen blow-pipe, or galvanic 
battery, is sufficient to fuse this metal. 



ALLOYS. 
_ . 684. The compounds of metals with 

Wliat is an 

alloy? Give metals are called alloys. The following 

ton C 7hrts are amon § the more important. 
and other al- Brass is copper lightened in color by 
the addition of one-fourth its weight of 
zinc. 

German silver is a kind of brass still further whitened 
by nickel. Its exact composition has been given in 
another place. An alloy of 30 parts silver, 25 of nickel, 
and 55 of copper forms a nearly perfect substitute for 
silver for all ornamental purposes. 



ALLOYS. 273 

Bronze is copper containing ten per cent, of tin. 
Bell metal is a kind of bronze containing tin in larger 
proportion. 

Pewter is an alloy of tin with variable proportions 
of antimony or lead. Britannia ware, so called, is a 
sort of pewter. 

Type metal is an alloy of lead containing twenty- 
five per cent, of copper. By the use of tin, instead of 
lead, a better, but more expensive type metal may be 
produced. Zinc, with a few per cent, of copper, lead, 
and tin, has also been recently employed. 

Fine and coarse solders are alloys of tin and lead 
the former being two-thirds, and the latter one-fourth, 
tin. Hard solder is a variety of brass. 

Newton's fusible metal, which has the remarkable 
property of melting in boiling water, is composed of 
8 parts of bismuth, 5 of lead, and 3 of tin. 

Many of the above alloys are slightly varied in 
their character by the addition of other metals in small 
quantity. 



274 



SALTS. 



Whatcom- 



CHAPTER III. 

SALTS. 

SOLUTION AND CRYSTALLIZATION. 

685. Definition. — Under the general 
pounds are head of salts, are included all compounds 
of acids and bases, and beside these, the 
compounds of chlorine, bromine, iodine, sulphur, &c. 
with the metals. Sulphate of soda or blue vitriol is 
an example of the first class, and chloride of sodium 
or common salt of the latter. 

686. Preparation of salts. — The salts 

Mention some 

methodsofpre- of most acids may be produced by sim- 
paring salts. ^ bringing the acid and oxide together. 
Sulphate of potassa is thus produced from sulphuric 
acid and potassa. Heat is sometimes required to bring 
about the combination. They may also be prepared 
from the carbonates. Thus acetate of lime, is pro- 
duced by pouring strong vinegar on chalk, or carbo- 
nate of lime. Carbonic acid is in such cases expelled 
by the stronger acid which is employed. Other meth- 
ods of preparing individual salts will be hereafter 
given. 

Explain &olu- 687. Solution. — The particles of all 

tlon " bodies are held together, as before ex- 

plained, by the attraction of cohesion. But water has 



SOLUTION. 275 

also an attraction for these particles. In the case of 
many substances, it overcomes the force of cohesion 
and distributes them throughout its own volume. 
Such a distribution, in which the solid form of the 
solid is entirely lost, is called solution. Different 
liquids are employed as solvents for different sub- 
stances. A solution is said to be saturated when no 
more of the solid will dissolve in it. 

688. Precipitation. — In solution, the 

Have the par- - it- 

tides lost their particles of bodies have not lost their 
tractiZthow property of cohesive attraction. It is only 
may they be overcome by a superior force. As soon as 

precipitated? . 

this is weakened they unite again to form 
a solid. The solvent power of alcohol for camphor, is 
thus diminished when water is added to the solution. 
As a consequence, the camphor immediately re- 
assumes the solid form. When a solid is thus 
re-produced as a liquid, it is called a precipit- 
ate. The above experiment is made by ad- 
ding water to an ordinary solution of camphor. 

689. One case of precipitation is men- 

Mention two , . , , . 

general meth- tioned in the preceding paragraph. But it 
ods of predp- ma y ^ e e ff ec ted by various methods. All 

tzation. 

of these may be arranged under two heads ; 
precipitation by changing the character or quantity of 
the solvent, and precipitation by changing the sub- 
stance dissolved. 

Mention three 69 °- CHANGE OF SOLVENT. The three 

cases of pre- cases i n which precipitation is effected bv 

cipitation by L * J 

change of sol- changes in the so vent, are. mixing, cooling, 
and evaporation. The first has just been 




276 SALTS. 

described. The second is illustrated in the production 
of alum crystals by cooling a hot solution. The third 
consists in dissolving a solid in some liquid and then 
boiling away the latter. The experiment may be tried 
with a saturated solution of salt and water. As fast as 
the water is boiled away, the portion which has lost its 
solvent re-assumes the solid form. 

691. Change of substance dissolved. 

Describe two . . . . 

cases by The change m the substance dissolved, is 

ttance 6 °^ mb ' e ^ ecie ^ in some cases by addition, and in 
others by subtraction. Carbonic acid 
blown through lime water precipitates it by addition. 
The precipitate is chalk or carbonate of lime. Pot- 
ash added to a solution of sulphate of copper, precip- 
itates it by subtraction ; the precipitate is oxide of 
copper, deprived of its acid by the potash. 

692. Explanation. — The above cases 

State the cause .... -. r 

of precipita- of precipitation demand some further ex- 
Hon in the planation. As fast as carbonic acid is blown 

above cases. r 

into the lime water, in the first case, the 
new substance chalk or carbonate of lime is produced 
throughout the liquid. We may suppose that innume- 
rable particles are first formed, before they unite to 
form a precipitate. But the cohesive attraction put 
forth by the particles of this new compound is so great 
that the opposing attraction of the water is overcome, 
they rush together, and assume the solid form of a pre- 
cipitate. This did not happen in the case of lime alone, 
because the cohesive attraction between its particles is 
inferior to the opposing attraction of the water. The 
second case is to be similarly explained. 



COHESION. 277 

wm . , 693. Relation of cohesion and affin- 

What is said • 

of the relation ity. — 1 he chemical affinity of potassa for 
YffdaffinUu? carbonic acid is evidently greater than that 
of lime. The former base retains the acid 
so firmly that no degree of heat can effect it, while 
the latter gives up its acid with readiness, under the 
influence of a high temperature. Notwithstanding the 
superior affinity of potassa, lime will take from it its 
carbonic acid, if added to a solution of carbonate of 
potassa in water. The mixture being made, the par- 
ticles in this and in all similar cases tend to re-arrange 
themselves in the solid form. They seem to do this 
without reference to their chemical affinities, in such a 
manner as best to resist the solvent action of the water 
or other liquid. Carbonate of lime resists such action 
better than carbonate of potassa. The former is there- 
fore produced. The cche ion of carbonate of lime, 
using the term in the sense of capacity to resist the 
separating power of water, has therefore determined 
the production of this substance in opposition to or- 
dinary chemical affinities. 

694. The above case illustrates a gene- 

Statc and il- 

lus'ratethe ral law. Two substances, which when 
general law. an i te( j f orm an insoluble compound, gen 

erally unite and produce it, when they meet in so 
lution. To illustrate by another example : phos< 
phate of lime or bone ash is insoluble. Ther 
we may be sure that phosphoric acid and lime, if 
brought together by mixing two solutions, will de- 
sert any substances with which they were before 
combined, and unite to form insoluble phosphate of 

12* 



278 SALTS. 

lime. This rule is not without exceptions, but it 
enables the chemist to determine beforehand innume- 
rable cases of precipitation. 

695. Solution and chemical combina- 

How does solu- . n . „ r . , 

Hon differ tion. — Solution differs from chemical com- 
from chemical bi na tioii in the varying proportions in 

combination f # J ° * ■ * 

which it occurs according to tempera- 
ture, and in the absence of any change of chemica* 
properties. Nitre, for example, dissolves in water at 
100°, in nearly double the quantity which will dis- 
solve at 70°. At the same time, it forms a solution to 
which it has imparted its own chemical properties 
unchanged. 

596. Another important distinction is 

State another . 

important found in the following fact. While chem- 
distinctwn. ical com bi nat j on i s most ac tive between 

bodies whose properties are most opposed, such as acids 
and bases, solution occurs most readily in the case of 
similar substances. The metals dissolve in mercury. 
Salts dissolve in water. Fats and resins dissolve in 
alcohol and ether, which, like themselves, contain much 
hydrogen. 

697. Crystallization. — In passing from 

What is said ,,..-, , ., 

of crystalline the liquid to the solid condition, the par- 
arrangement? ti ~ leg ^ ^^ bodies assume a crystalline 

arrangement. Their mutual attraction is more than 
a mere force which draws and binds them together. 
It groups them in regular forms. The crystals thus 
produced are often too small to be separately seen. But 
even where this is the case, the crystalline structure is 
readily observed. Surfaces of zinc or cast iron ex- 



CRYSTALS. 



279 



posed by recent fracture, are fami iar examples. But 
where the circumstances are favorable for the forma- 
tion of individual and separate crystals, the most beau- 
tiful and symmetrical forms are often the result. 

698. Production of crystals. — Most 

How may 

cri/stals'be of the salts to be described in this chap- 
proc ua . ter ma y k e obtained [ n t h e f orm f crys- 
tals by evaporating or cooling their saturated 
solutions. The method by cooling has already 
been described in the chapter on Water. In 
obtaining crystals by evaporation, the solution 
is to be moderately heated in a saucer or other 
vessel. The crystals formed by either method 
commonly contain water, which becomes part of 
the solid crystal, and is called water of crystalliza- 
tion. 

699. Variety of crystals. — The forms 
of leaves and flowers are scarcely more va- 
rious than those of crystals. The latter are, 
as it were, the flowers of the mineral world, 

as distinctly characterized in their peculiar beauty as 
the flowers that bloom in the air above them. Even 
where color fails, the eye of science distinguishes pe- 
culiar features which often enable it to determine the 
nature of a substance from the external crystalline form 
which it assumes. 

12 3 4 5 



How may the 
variety of 
crystals be il- 
lustrated ? 




J 




280 SALTS. 

What i* said 700 - FoRMS 0F crystals.— As every 

of the variety flower has its own distinctive form of 

of forms in a . 

single sub- leaves and petals, so every substance has 
its own form or set of forms from which it 
never essentially varies. Among these or its combi- 
nations, it is, as it were, left free to choose in every 
crystal which it builds. The mineral quartz, which 
caps its prismatic palace with a hexagonal pyramid, is 
an example. Its common form represented in Fig. 4, 
is a combination of the prism and double six-sided py- 
ramid, which commence the series. 

701. A form similar to the double six- 

D escribe some 

forms of a sided pyramid, with faces corresponding to 
single set. -^ twe | ve converging edges, belongs to the 

same set. Double pyramids similar to each of these, but 
of one-half or one-third their relative height, or differing 
from them by some other simple ratio, also belong to 
the same set of forms. Fig. 3 represents a form com- 
posed of two of these pyramids. Fig. 5 represents 
another form in which one of them is modified by two 
faces of a prism. To all of these and certain other in- 
timately related forms, the imaginary privilege of se- 
lection and combination, above referred to, extends. 
But most substances, like quartz, as above described, 
affect some particular shape or combination in which 
they usually appear. 

702. Modifications of crystals. — 

What modifi- „ Ti • /• , . . . 

cationsofthe Whatever the form or combination may be, 
same form ^ - susceptible of variation, in any degree, 

may occur ? l ' J ~ ' 

so long as its angles correspond to those of 
the perfect shape. Thus the mineral quartz, in its 



CRYSTALS. 



281 





J 



commonly occurring combination, is not restricted to a 
perfectly symmetrical shape, like that above presented. 
It may develop one surface and diminish the others to 
any extent. Forms such as 
are represented in the margin 
result. Diffeient as they seem, 
it will be observed that they 
agree precisely with the per- 
fect, shape in the angles be- 
tween the surfaces of the prism and pyramid, and the 
different surfaces of each. In this their identity 
as crystalline forms consists. It would thus seem that 
nature pays exclusive attention to the corners and an- 
gles in her various systems of crystalline architecture. 
703. The least variation of the relative 

What consti- 
tutes a ?icw length of the vertical axis that is not by 

some simple ratio, constitutes a new and 

distinct form. This has its related forms as before, 

the whole making a new and distinct set, to which the 

choice of any substance that enters it is limited. 

n „ 704. Systems of crystal forms. — It 

Define ano- 
ther system of will be obvious to the student that the sub- 

C forms. lUe stitution of an octahedron, such as is re- 
presented in the accompanying figure, for 
the double six-sided pyramid, would be the 
starting point of an entirely distinct system of 
forms. Within its limits there might be in- 
numerable sets as before. It would be, as it 
were, the type o f a new order of crystalline architec- 
ture, susceptiN yf variations consistent with the ge- 
nera) styl* 




282 



SALTS. 



Define the 
third and 
fourth 
systems. 



705. A third system is characterized by 
inequality in three principal dimensions. 
The axes or lines connecting the solid an- 
gles in the octahedron, and joining the faces in the 
prism, are all unequal. As each axis may be indefi- 
nitely varied in this system, there is room wthin its 
limits for still greater variety than before. The fourth 
system differs from the third in an oblique position of 
some one of the unequal axes. The student will 
readily imagine certain oblique forms which it m 
eludes. The fifth system is characterized by an ob 
lique position of three unequal axes.* 





Wh ^^' ^^ e re S u ' ar system, which is pro- 

characteristics perly the first, has all its axes equal and all 

%s?eL7 Ular its an S les ri S ht angles.f The fibres 
which precede this paragraph represent 
some of its simpler forms. Those which follow, are 
among its most interesting combinations. In the 
last, the student will be able to select three distinct 
kinds of surfaces. One of these sets, if enlarged to 
the exclusion of the others, would produce a cube, 

* The variations of length and inclination of axis which correspond 
to the different systems, may be beautifully illustrated to the eye by a 
wooden frame work movable at the centre with threads connecting 
the arms. 

f The first and sixth systems are made to change places in the above 
arrar gement, for the convenience of illustration from the quartz crystal. 



CRYSTALS. 2S3 



another a regular octahedron, and a third a dodecahe- 
dron ; forms corresponding to those of the preceding line. 




In view of its simplicity, the regular system may be 
regarded as a sort of primitive architecture, yielding, 
however, to no other system in the beauty of its forms. 
Under one or the other of these systems all forms of 
crystals are included. To each of them, with the ex- 
ception of the last, belong innumerable sets of forms 
according to the degree of inequality or inclination of 
the axes. Equality and rectangular position of the axes 
being characteristic of the first system, it is not suscep- 
tible of the sort of variation which is essential to pro- 
duce different sets of figures. But in this, as in other 
systems, the modification of surfaces may occur to any 
extent. 

Show how tk» 7®7* ^ S ^ e arc hitect is able, from some 
formofacrys- relic of a broken column, to build up in 
ferTedfrom 1 imagination the temple of which it formed 
its angles. a p art . as t h e comparative anatomist knows 
how, from the fragment of a single bone to reconstruct 
in imagination the perfect animal which possessed it ; 
so, from the merest point of a crystal, its complete form 
may often be readily inferred. In proportion as a dou- 
ble pyramid is lengthened out, the angles above and 
below are rendered more acute. From an accurate 
admeasurement of this angle its whole shape may there- 
fore be inferred. Such admeasurement 'f various an- 



284 



SALTS. 



gles is employed not alone as a means of inference of 
perfect from imperfect shapes, bat as the simplest means 
of accurate description. For, as before stated, it is the 
size of the corresponding angles of a crystal which 
form its characteristic 

Have different 708. Isomorphism. — Many substances 
substances ever w hj c h are a jjfc e { n t h e num ber and arran^e- 

the same crys- 5 

tallineform? ment of their atoms, although these atoms 
are different in kind, have the same crystalline form. 
This is the case with common alum and other alums 
to be hereafter mentioned. The similar arrangement 
of atoms will be best seen by inspecting the formulae 
which represent them. These are given in the appendix. 
The term expresses their likeness in form. Besides 
this series there are many other isomorphous groups. 
Give the pro- 709. It is to be regarded as probable, 

bable reason. t } iat ^ s h a p e an( J s j ze f the molecules 

thus similarly composed is exactly the same, and that 
it is for this reason that they may be used in building 
up crystals of the same form. The different alums will 
even unite when they crystallize in building up one 
and the same crystal. Substances which are thus si- x 
milar in composition and crystallize in the same form, 
are called isomorphous. There are many cases of simi- 
lar crystalline form in substances which are not thus 
related in other respects. Such bodies are not called 
isomorphous, notwithstanding their identity of crys- 
talline form. Certain substances crystallize in forms 
belonging to two or even three different systems, ac- 
cording to the temperature, or other circumstances 
under which their crystallization occurs. Such sub- 
stances are called dimorphous or trimorphous. 



oxides. 285 



OXIDES. 



Define an ox- 710. The compounds of the metals with 
fetms^dtf- ox yg en > with the exception of those which 
ferent oxides have decidedly acid properties, are called 

distinguished? 

oxides. When a metal unites with oxy- 
gen in several different proportions, forming different 
oxides, these are distinguished as protoxide, deutoxide 
or binoxide, tritoxide or teroxide :. terms signifying 
first, second, and third oxides. The highest oxide is 
also called peroxide. An oxide containing three atoms 
of oxygen to two atoms of metal, is called a sesquiox- 
ide. The names of chlorides, sulphurets, &c. are simi- 
larly modified, to indicate the proportion of chlorine, 
sulphur, &c. which they respectively contain. Com- 
pounds of non-metallic substances with oxygen which 
do not possess acid properties, are also called oxides. 
There are, for example, oxides of nitrogen and phos- 
phorus. 

711. Properties of oxides. — The 

What is said - . .. ,, , 

of acid and lower oxides are generally strong bases, 
baste proper- w hji e t ] ie higher oxides exhibit basic or 

tics in oxides f ° 

acid properties according to circumstances. 
Binoxide of tin, for example, described m a previous 
chapter, acts as a base in combining with sulphuric 
acid to form a sulphate, while, if fused with potassa, it 
acts as an acid and forms a stagnate. On account of 
its acid property, the binoxide of tin is also called stan- 
nic acid. The name is derived from Stanmim, which 
is the Latin word for Tin. 



286 oxides. 

712. Formation of oxides. — Oxides 

Hoxo are ox- 
id** formed ? may be formed directly by the union of 
Give exam- oxygen and metal, or, indirectly, by sepa- 
rating them from some salts which con- 
tain them. Thus oxide of copper may be produced 
by simply heating copper in the air ; or, by precipita- 
tion from the nitrate, through the agency of potassa, 
or, thirdly, by simply heating the nitrate till all the 
acid is expelled. The oxides of tin and antimony are 
also directly produced, by the action of nitric acid on 
the metals. 

What is a hy- 713. HYDRATES, OR HYDRATED OXIDES. 

drated oxide? Oxides commonly combine in the act of 
precipitation with a certain proportion of water. The 
compound thus formed are called hydrated oxides, or 
simply hydrates. The water may, in most cases, be 
separated from them by heat, and the uncombined 
oxide thus obtained. 

714. Conversion of oxides. — When 

What i ^ *iaid 

of the lonver- oxides are converted into chlorides, sili- 
con of oxides? phuretSj ^^ by double decompositions, to 
be hereafter described, the chlorides, sulphurets, &c, 
correspond to the oxides from which they are formed. 
Thus, protoxide of iron yields protochloride, while ses- 
quioxide yields sesquichloride. 

715. The alkalies. — The oxides of po- 

Give some . it n i „ »• 

•properties of tassmm and sodium are called alkalies. 
the alkahes. ^bey are k nown as po tassa and soda, 
and are commonly obtained as hydrates. They are 
white infusible substances from which the water 
cannot be expelled by heat. They are soluble in water, 



POTASSA. 287 

and are the strongest of all bases. From their destruc- 
tive action on animal matter, they are called caustii 
alkalies, and are often distinguished by this term 
from the carbonates of potassa and soda. 

POTASSA. 
716. Potassa is prepared from wood 

What is the % ; r 

source of po- ashes. The ley obtained from these be- 
ing evaporated to dryness, the mass which 
remains is the crude potash of commerce. This, when 
purified, becomes pearlash. 

How is potassa 717. Caustic potassa. — Commercial 

prepared? potash and pearlash are both carbonates 
of potash, from which the carbonic acid must be 
removed, in order to produce potassa itself. This is 
done by a milk of slaked lime. A solution of potash 
in at least ten parts of hot water, or a hot ley, made 
directly from wood ashes, should be employed in the 
experiment. To this the milk of lime is added, little 
by little, the solution boiled up after each addition, 
and then allowed to settle. If, after settling, a por- 
tion of the clear liquid is found no longer to effervesce 
on the addition of an acid, it is sufficient evidence 
that all the carbonic acid has been removed by the 
lime, and the process is completed. This must be as- 
certained by trial. About half as much lime as pot- 
ash will be required in the process. Caustic soda is 
similarly made from the carbonate of soda. 

718. The boiling in the above process 

Give a modi- . r 

ficailon of the may be omitted, if the mixture be fre- 
abovc method. q Uent ] y s haken up during several days. 

13 



288 



OXIDES. 




This modification of the method is much the most 
convenient for the production of caustic al- 
kalies in small quantities. Solutions, useful 
for a variety of chemical purposes, are thus 
obtained, and should be preserved for use. 
They may be converted into solids by 
evaporation, and the solid thus obtained fused 
and run into moulds. The commercial caustic 
potassa, occurring in slender sticks of white 
or grey color, is thus produced. 

719. Affinity of potassa for water. 

How can the 

affinity of po- Ordinary potassa, as before stated, 
I7p°tjdt ter is a hydrate. But its affinity for 
water is by no means yet satis- 
fied in this form. If exposed in an open 
vessel, it rapidly attracts moisture from the 
air. It often dissolves, in the course of a few days, in 
the water thus obtained. 

720. Decomposition by potassa.— Po- 
tassa added to the solution of almost 
any salt occasions a precipitate. The 
potassa takes the acid and precipitates the 

insoluble base. If the experiment is made with an 
ammonia salt, the base being volatile passes off into 
the air. Experiments may also be made with green, 
blue, and white vitriols, which are, respectively, sul- 
phates of iron, copper, and zinc. 

721. Cleansing and caustic proper- 
Mustrate the P0TASSA ._if so iled rags are boiled 

cleansing pro- ilL3 vx *%***>>* D 

perties of po- w j t h a dilute solution of potassa, they will 
be thoroughly cleansed by the process. 




What is said 
of the decom- 
position of 
salts by po- 
tassa ? 



tassaf 



POTASSA. 289 

The potassa unites with the acid of the grease con- 
tained in the cloth, and thus makes it soluble in water. 
722. Action of potassa on animal 

What is the . 

action ofpo- matter. — Potassa is extremely destructive 
tassa on am- f an i ma i ma ttei\ It readily dissolves the 

mat matter ? J 

skin, as may be proved by rubbing a little 
between the fingers. If applied in sufficient quantity, 
it destroys the vitality of the flesh. It is often used 
for this purpose by surgeons. 

723. Effect on vegetable oolors. — 
tassa affect vc- Vegetable blues which have been pre- 
fetable colors* v i 0U sly reddened by acid, are restored to 
Iheir original color by the action of potash and other 
alkalies. The blue pigrc^nt called litmus is the one 
most readily obtained. In preparation for the exper- 
iment, it is infused in hot water The transformation 
from blue to red and vice versa may be repeated as 
often as desired, by the alternate addition of acid and 
alkali. Paper soaked in the red and blue liquids 
forms the test-paper of the chemist. It is used to in- 
dicate the presence of smaller quantities of acid and 
alkali than could be recognized by the taste. An extract 
of purple cabbage leaves, or the leaf itself, may be 
used in the above experiment. In this case the change 
of color by alkalies is from red to green. 
„, T m , 724. Properties of soda. — The prop- 

What of the ^ l 

properties of erties of soda are very similar to those of 
potassa, as above described. 



18 



290 



OXIDES. 



OXIDE OF AMMONIUM. 



What is said 



725. Formation. — When hydrated 
of oxide of sulphuric acid combines with ammonia, 

ammonium? the water whkh jj. contains ig reg arded 

as converting the ammonia into oxide of ammonium, 
with which the acid then combines. The action of 
other hydrated acids is the same. In naming the cor- 
responding salts, the oxide of ammonium is called 
ammonia. Thus, the compound with sulphuric acid, 
is called sulphate of ammonia. It is to be borne in 
mind, that oxide of ammonium of such salts, contains 
a molecule of water in addition to the constituents of 
ammoniacal gas. 

OXIDE OF CALCIUM. 

How is lime 726. Lime. — Lime or oxide of calcium 

obtained? is best obtained by heating chalk, marble 
or limestone. These are all carbonates of lime. Under 
the influence of a high temperature, the tendency of 
the carbonic acid to assume the gaseous form is so 
increased, that the chemical affinities of the base are 
overcome. The carbonic acid escapes, leaving the caus- 
tic lime behind. This is the process of the ordinary lime 
kiln. The superior strength of potassa and soda as 
bases, is illustrated by the fact that the carbonic acid 
cannot be removed from them through the agency of 
heat. 

727. Hydrate of lime. — Slaked lime. 

What is hy- _ 

drate of When water is added to lime, one equiva- 

lent immediately combines with it and 



LIME. 291 

forms a hydrate. The hydrate, like that of potassa, is 
dry, although it contains a large portion of combined 
water. As the water thus becomes solid in the com- 
pound, its latent heat is given off to the air or sur- 
rounding objects. The employment of heat thus pro- 
duced for culinary operations has been recently sug- 
gested. If the process of slaking is conducted 
under a tumbler, with a slight surplus of water, steam 
will be produced. On lifting the tumbler, it will be- 
come visible by its condensation into vapor. 
__ 728. Ignition by lime. — The heat 

How may gun- . . . 

powder be ig- thus produced is often sufficient to ignite 
tfaX^of gun-powder. It should be sprinkled on 
lime? the mass and kept dry while the slaking 

proceeds. Warm water and well-burned lime should 
be employed in the experiment. 

729. Action of the air. — If lime is 

What is the 

action of the exposed to the action of the air, it gradu- 
al <m^/ie; ^ combines with carbonic acid and 
water, and becomes converted into a mixture of hydrate 
and carbonate. It is then called air-slaked lime. By 
sufficiently long exposure the conversion into carbo- 
nate is complete. 

730. Lime in mortar. — Ordinary mortar 

Why does . . T , , 

mortar har- is a mixture of sand and lime. It hardens 
denf not simply by drying, but by the absorp- 

tion of carbonic acid from the air. A compound of 
hydrate and carbonate of lime, possessed of great hard- 
ness, is thus produced. A gradual combination also 
takes place between the silica and the lime, which 
binds the two constituents still more firmly together 



292 OXIDES. 

731. Hydraulic cement. — If, in the 

Wliat is hy- 
dra ic ce- preparation of lime, a limestone is used 

ment? which contains a certain proportion of 

clay, a double silicate of alumina and lime is produced. 
The compound has not alone the property of combi- 
ning with water, like ordinary lime, but of becoming 
extremely hard and insoluble in the process. Such a 
lime is called hydraulic cement, and is used for building 
under water. Silica, magnesia, and some other sub- 
stances impart the sime property to lime. 

ALUMINA, MAGNESIA, <fcc. 

Whatisalu- 732. Alumina, &c. — Alumina, so named 
mum? from the corresponding metal, is insoluble, 

and is called an earth. It is, like the peroxide of iron, 
a sesquoxide, containing three atoms of oxygen to two 
of metal. Natural alumina colored blue is called sap- 
phire. Colored red it forms the oriental ruby. The 
topaz and the emerald are also compounds containing 
the same oxide. Baryta, strontia, lime and magnesia, 
are regarded as standing midway between the earth 
alumina and the alkalies and are called alkaline earths. 
They are more or less soluble, and possess the general 
properties of the alkalies in a diminished degree. 
Magnesia is sometimes classed as an earth. 

733. Other metallic oxides. — The 

What are the , . .. r 

properties of remaining metallic oxides are powders oi 
feather me- different colors . Most of them are insol- 

tactile oxides ? 

uble. The more important have been 
already noticed in the Chapter on Metals. Their 



USES OF OXIDES, j 293 

hydrates may be obtained by precipitating solutions 
of their salts with potassa, soda, or ammonia. The hy- 
drate of the oxide oi copper and peroxide of iron 
may serve as examples. The former is blue and the 
latter a reddish brown. 

734. The hydrated oxides of nickel, co- 
te*/ oxides dis- bait, tin and copper, produced from solu- 
te maw- t j on f ^ ese me tals by the addition of 

ammonia, are again re-dissolved in an 
excess of ammonia. That of copper dissolves with a 
beautiful blue color, which is conclusive evidence that 
the liquid with which the experiment is made contains 
copper in solution. 

735. Uses. — Oxide of magnesium or 

Give the uses 

of some of the magnesia, and mercury, among others, are 
oxides, used in medicine, and white oxide of zinc, 

as a paint. Litharge or protoxide of lead is employed 
in making flint-glass and varnishes. Red lead is used 
as a paint. Oxide of bismuth is employed as a cos- 
metic. 

736. Oxide of manganese is used to 
JrltcetL" color § lass P ur Ple ^id violet. Oxide of 
glass by the cobalt, to color it blue ; oxides of copper. 

oxide of man- - 

ganese, cobalt, and chromium, to impart a green color to 
&c P &c l™' §^ ass an( ^ P orce l a in : peroxide of iron, 
to give it a yellowish red, and protoxide, a 
bottle-green. Sub-oxide of copper gives to glass a 
beautiful ruby red. Silver and antimony are employed 
to produce different shades of yellow and orange. Vi- 
olet and rose color are obtained by means of the purple 
of cassius, a beautiful purple precipitate, containing 




294 CHLORIDES. 

tin and gold, and prepared by adding protochloride of 
tin to a gold solution. 

737. Glass staining. — The effect of 

How may these . . 

effects be illus- oxides, above mentioned, m coloring glass, 
trated? ma y ^ Q in us t ra ted by fusing them into a 

borax bead. The bead is to be formed with the 
aid of the blow-pipe, in a loop of platinum wire. 
In the absence of such wire, the borax glass 
may be made upon the surface of a pipe bowl. In- 
stead of employing the oxide, it is generally more 
convenient to moisten the bead with a very small 
quantity of a solution of the metal. In order to obtain 
good colors, the quantity of coloring material employed 
must be very small. 

738. For staining glass and porcelain su- 
and porcelain perficially, a colored and easily fusible 
tidalf ? Uper ~ §" ass * s ^ rst prepared with borax or some 

analogous material. This being ground 
up and applied as a paint, is afterward baked into 
the surface. Several of the oxides mentioned in a pre- 
ceding paragraph are thus employed. 

CHLORIDES. 

739. Description. — The chlorides are, 

Describe some 

of the proper- for the most part, soluble salts, of colors 
tl fs°f chl °' corresponding to the solutions of the metals 
from which they are produced. Common 
salt may stand as a type of the class. Chlo- / 
ride of silver and subchloride of mercury or [ 
calomel are insoluble ; the chloride of lead is [ 
but lightly soluble in water. 



CHLORIDES. 295 

740. Preparation. — Chlorides may be 

How are Mo- i i , • r i i i i 

rides made made by the action of chlorine or hydro- 

from metals? chloric acid Qn ^ met als. The COmbllS- 
drive examples. 

tion of antimony in chlorine gas, the solu- 
tion of gold in aqua regia, and that of zinc in hydro- 
chloric acid are examples. The chemical action in each 
of these cases has been explained in previous chapters. 
The solutions being evaporated, the chlorides are ob- 
tained in the solid form. The solution of zinc in hy- 
drochloric acid is a case of single elective affinity: 
the metal elects or chooses the chlorine. 

741. Chlorides may also be formed by 

How are chlo- 
rides produced the action of hydrochloric acid on oxides. 

fromoxi s. Thus common salt or chloride of sodium 
may be made by mixing hydrochloric acid and soda. 
The hydrogen of the acid and the oxygen of the soda 
unite to form water, while the chlorine of the acid and 
the metal sodium unite to form the chloride. This is 
a case of double decomposition, resulting from doable 
elective affinity. The chloride commonly corresponds 
to the oxide from which it is produced. Thus soda, 
which is a protoxide, yields common salt, which is a 
protochloride. Again, sesquioxide of iron, containing 
three atoms of oxygen to two of metal, yields sesqui- 
chloride of iron containing the same proportion of chlo- 
rine. 

How are the 742. The insoluble chlorides may be ob- 

insolubie chlo- tained directly in a solid form by a similar 

rides obtained 

directly in a double decomposition. Thus, chloride of 
so id form? so dium and oxide of silver in solution, 




296 CHLORIDES. 

yield, when mixed, a precipitate of chhride 
of silver ; newly-formed oxide of sodium or 
soda remains in solution. The latter unites 
with the acid originally employed to dissolve 
the Dxide of silver. This is commonly nitric 
acid. 

743. Chloride of sodium. — Common 
sources is com- salt. — Common salt is found in great 
^obtained? abundance in Poland and other countries, 

as Rock salt, which is regularly mined like 
coal. It is also obtained by evaporating the water of 
the sea or salt springs, in the sun or by artificial heat. 
When the salt water is boiled down the salt separates 
in crystals, while the impurities remain in the small 
portion of liquid which is not evaporated. These con- 
sist principally of chloride of magnesium and other 
salts. Contrary to the general rule, salt is equally solu- 
ble in cold and hot water. 

744. When salt is to be made from 

How is salt . ... 

produced from water which contains it in very small pro- 
¥ r y™ ak portion, it is a frequent practice in Europe, 

to pump the weak brine to the top of large 
heaps of brush, and allovv it to trickle through them. 
The object of the method is to produce a large evapo- 
rating surface. The air, as it passes through the heaps, 
carries away a large part of the water and leaves the 
fait behind. The strong brine which is collected below 
is then boiled down, as before described. The annual 
produce of the salt springs at Syracuse, New York, ex- 
ceeds 5,000,000 bushels. 




CHLORIDE OF SODIUM. 297 

745. Beautiful crystals of common salt 

How may cry s- . , _ 

fob o/*aft 6e may be obtained by gradually evaporating 
oftfom**/ a saturate( ] solution. This will be accom- 

plished by keeping it for some time moderately warm 
on a stove or in the sun. The crys- 
tals are shaped as represented in the 
figure, and are made of innumerable 
small cubes, which build themselves 
regularly upon the edges as the larger crystals sink 
little by little into the solution. 

746. Uses of common salt. — The use 

How does salt . 

act to preserve of common salt m preserving the flesh of 
fi e9,h ' animals from decay, depends in part on 

the fact that it extracts from the flesh a large propor- 
tion of water. It thus, to a certain extent, dries them. 
This action will be immediately observed if a little 
salt is sprinkled upon flesh. It will speedily draw 
out the juices of the meat and itself disappear by dis- 
solving in them. 

How much salt U7 - Sea water.— Every pound of sea 
is contained in water contains from one-half to five- 

sea water? in . /* i^ mi 

the water of eighths of an ounce oi salt. 1 he greater 
the Dead Sea? p ar t f this is chloride of sodium or com- 
mon salt. The water of the Dead Sea contains a 
much larger proportion, and is more than an eighth 
part heavier than pure water. Owing to its greater 
density, a muscular man floats breast high in it without 
the least exertion. Fresh eggs, which sink in sea 
water, float in that of the Dead Sea with one-third of 
their length above the surface. 

13* 



298 chlorides. 

748. Chloride of lime. — Bleaching 

Qm, what does 

the value of powder. — The commercial article of this 
utTdep°td? name is P re P ared b y passing chlorine gas 
over lime. It is a white powder with an 
odor similar to that of chlorine gas. Its value depends 
on the fact that the gas is thus brought into a solid 
form and made capable of transportation. It may be 
released again by the simplest means, to be used as a 
bleaching and disaffecting agent. The addition of an 
acid, as has been seen in the chapter on Chlorine, is all 
that is necessary to effect this object. It occurs, in- 
deed, spontaneously in the moistened powder, through 
the action of the carbonic acid of the air. 

749. Illustration. — To illustrate its 
properties be bleaching power, a strip of calico may be 
illustrated? soa ked in a solution of the chloride, and 
then in acid water. Nascent chlorine is thus liberated in 
the fibre of the cloth, and is more effectual than if 
otherwise applied. 

750. Form of combination. — The che- 

How are its _ . . n 

elements com- mical action which occurs in the formation 
bmcd? f chloride f lime is as follows. The 

chlorine combines with both constituents of the lime 
forming with its metal chloride of calcium, and with its 
oxygen, hypochlorous acid. This acid combines as it 
is produced with another portion of lime forming a salt. 
Bleaching powder is therefore a mixture of chloride of 
calcium and hypochlorite of lime, with a certain pro- 
portion of lime still uncombined. The name chloride 
of lime has no chemical propriety. The mixture is, 
practically, chlorine and lime, for as soon as an acid is 



CHLORIDE OF ALUMINIUM. 299 

added, all of the original lime is re-formed and chlorine 

is evolved. 

■ . 7T 751. Chloride of aluminium. — This 

How is chlo- 
ride of alumi- salt is of peculiar interest and importance, 

paredV 6 ' * n Yiew °f ^ ts employment in the prepara- 
tion of the new metal aluminium. It is 
prepared by heating alumina at the same time with car- 
bon and chlorine. The alumina is torn asunder, as it 
were,, by the affinities which are thus brought into play. 
The carbon takes its oxygen and passes off with it as car- 
bonic oxide, while the chlorine takes the metal and es- 
capes with it as volatile chloride of aluminium. The 
carbon in the process is supplied by coal tar. The 
process is conducted in iron retorts, the materials hav- 
ing been previously ignited together before their intro- 
duction. 

How is it pu- "5%- The chloride is impure, from the 
rifled? presence of volatile sesquichloride of iron. 

This is separated by leading the uncondensed vapors 
over highly heated points of iron. The iron has the 
effect of removing part of the chlorine from the ses- 
quichloride of iron and reducing it to a non-volatile 
protochloride. It is thus stopped in its course, while 
the chloride of aluminium passes on unaffected. It con- 
denses in the cooler part of the apparatus, in the 
form of colorless transparent crystals. 

753. Colored flames. — A series of 

What is said . 

of colored *beautiiul name experiments may be made 

flames? ^^ the chlorides> The ft ame f alcohol 

assumes different colors according to the chloride em- 
ployed. Chloride of sodium or common salt gives 



300 SALTS. 

a yellow ; chloride of potassium, violet ; i it y\)\ i j 
chloride of calcium, orange ; chloride of IM/WW 
Darium, yellow ; chloride of copper, blue. <^^ykif^^^ 
Instead of the chlorides, other soluble 
salts may be employed with the addition of a little hy- 
drochloric acid. A beautiful green may be obtained 
from a copper coin moistened with strong nitric acid, 
with the use of alcohol as before. The colors of fire- 
works are similarly produced by the addition of the 
above and certain other salts. 

754. Other Chlorides. — The other 

WJiat is said . ■ . . 

of other ddo- chlorides are not of sufficient general m- 
ndes ? terest to be here particularly described. Cor- 

rosive sublimate, the uses of which are mentioned in 
the chapter on Mercury, is a chloride of this metal. 
Calomel is a subchloride of the same metal. 



IODIDES, BROMIDES AND FLUORIDES. 

755. The iodides and bromides are 

i\ ii o t i^ said 

of the iodides classes of salts analogous to the chlorides. 
andbromides? Those of p 0tassium? nsed in me dicine and 

in photography, are the most important. 

rr . T7 756. Detection of yooiooTr iodine. — 

How is the blue . - _ ■ . . __ 

iodide of A beautiful blue is prepared by adding a 

^ared?™' ^ u ^ e c hl° r i ne water and starch paste to a 
solution of iodide of potassium. The 
chlorine sets iodine at liberty, which then combines 
with starch to form the blue compound. By this test 
iodine ean be detected in a liquid which contains but a 




IODIDES AND BROMIDES. 301 

millionth part of this element. By the substitution of 
bromide of potassium in the experiment, an orange 
color is produced. 

How is this 7o7. Test for chlorine and iodine. — 

experiment rji^ experiment may also be made by 

employed as a x 

test for chlo- moistening a slip of paper with starch and 
rine? iodide of potassium, and holding it in an 

atmosphere containing a little chlorine gas. 
An extremely small quantity of chlorine is 
thus indicated, and the prepared paper thus 
becomes a test for chlorine. Such paper is 
also used to show the presence of ozone in 
the air. 

758. Change of color by heat. — By 

What is said 

oftheiodideof mixing solutions of iodide of potassium 
mercury. and corrosive sublimate or chloride of mer- 

cury, a beautiful scarlet iodide of mercury is produced. 
On heating the dried precipitate it becomes yellow. 
The experiment is best made with two watch glasses. 
The iodide is heated in the lower one and collects by 
sublimation, with changed color, in the upper. 
an * # * - 759. Change of color by touch. — 

What effect is 

prodded by Ou touching the yellow incrustation with 

touching the . . „ ,. _. , 

yellow incrus- the point ot a needle, it is immediately 
tation? stained scarlet at the point of contact. The 

color gradually spreads, as if it were a contagious dis- 
ease, through the whole mass, until every particle has 
regained its original scarlet. This experiment fur- 
nishes a very remarkable instance of change of an im- 
portant property without change of composition. As 



302 



SALTS. 



the change of color proceeds, the small soales of which 
the yellow iodide is composed break up into octa- 
hedrons. The change of color is regarded as a conse- 
quence of the re-arrangement of atoms, which produces 
the change of form. 

FLUORIDES. 

What is said ^60. Fluor-spar. — The fluorides, with 
of 'fluor-spar 7 ^ e exception of those of the alkalies, are 
for the most part white insoluble compounds. The 
only one of especial interest, is the beautiful mineral 
known as fluor-spar. This mineral is a fluoride of 
calcium. It is found of white, green, purple 
and rose color, crystallized in regular cubes 
or octahedrons. Hydrofluoric acid, which has 
the remarkable property of etching glass, as 
before described, is prepared from it. 

SULPHURETS. 

Define a sul- 761. The compounds of the metals with 
phuret. sulphur are called sulphides or sulphur ets. 

They are of various colors, and, for the 
most part, insoluble. Iron pyrites and ga- 
lena or sulphuret of lead, are examples. 
The figure represents a crystal of magnetic pyrites, 
which is one of the sulphurets of iron. The form be- 
longs to the sixth or hexagonal system. 

762. Preparation. — Most of the sul- 

How are sul- , 

phuret* gene- phurets may be produced by adding hydro- 

ra areJf e ~ sulphuric acid to solutions of the different 

metals or their salts. Sulphur and metal 




SULPHURETS. 303 

unite and precipitate, while the hydrogen and oxygen, 
previously combined with them, form water. 
Mention the 763. The sulphuret of zinc is white ; 

colors of some that f arsen i c yellow ; and that of anti- 

of the sulphu- ' J ; 

rets. mony, orange. The remainder of the in- 

soluble sulphurets are black. Solutions of 
white vitriol, arsenious acid, and tartar emetic 
may be used, as above directed, to produce sul- 
phurets of zinc, arsenic and antimony. If 
the zinc precipitate should be colored, it is 
owing to the presence of iron in the salt, as 
impurity. Blue vitriol may be employed to produce 
black sulphuret of copper. 

764. The sulphurets of ammonium, po- 

What is said . . 4 . . 

of the sulphu- tassmm and sodium cannot be precipitated 
ZkaUes^ 6 fe y this process. Being soluble, they re- 
main in the liquid. Solutions of the caus- 
tic alkalies are to be used in preparing them. The so- 
lutions of these sulphurets are useful, as they may, in 
many cases, be substituted with advantage for hydro- 
sulphuric acid in precipitating sulphurets from solutions 
of other metals. Certain other sulphurets are soluble 
and do not precipitate, as will be seen from the table 
in the Appendix. L 

765. Liver of Sulphur. — There are a 

What is liver . r . . r 

of sulphur? number of sulphurets of potassium, con- 
How l s ? lt pre ~ taining each a different proportion of sul- 
phur. That which contains five atoms of 
sulphur to one of metal is called, from its peculiar 
color, liver of sulphur. It is prepared by boiling flowers 
of sulphur in a strong solution of potash. It may also 



304 SALTS. 

be made by fusion of the same materials. The proto- 
sulphuret can be made from the sulphate, by reduction 
with hot carbon. Certain other soluble sulphurets may 
be produced in the same manner. 

766. Milk of sulphur. — This form of 

How is milk of . . . 

sulphur pre- sulphur, like that just mentioned, is used 
pared? j n me( jj c i ne< Jt ma y be prepared from a 

solution of the liver of sulphur, by the addition of an 
acid. The latter combining with the potassa, the sul- 
phur is precipitated in a state of the finest division, 
giving to the liquid the appearance of milk. 

767. Other Sulphurets. — The natu- 
of the other ral sulphurets have colors different from 
sulphurets? ^ e similar compounds when produced, as 
above, by precipitation. Thus, the natural sulphuret 
of lead or galena has the color of the metal ; that of 
mercury is red, and is called cinnabar ; that of zinc, 
called zinc blende, and by miners black jack, is of dif- 
ferent shades — brown, yellow and black. The precipi- 
tated sulphuret of mercury turns red by sublimation, 
and in this state forms the familiar pigment called ver- 
milion. Sulphuret of iron, which is employed in 
making hydrosulphuric acid, may be prepared by hold- 
ing a roll of sulphur against a rod of iron previously 
heated to whiteness. This may be readily done in any 
blacksmith's shop. The fused sulphuret falls in glo- 
bules from the surface of the iron. 



SULPHATES. 305 

SULPHATES. 

768. The sulphates, with the ex- 

What is said . _ _ _ __ _. 

of the color ception oi those of the alkaline 

7*$ES earths > are > for the most p art > solu - 

ble salts. They are similar in color to 
the solutions of the corresponding metals. The 
figure represents a crystal of gypsum. The form be- 
longs to the fourth system. 

769. Preparation. — The sulphates are 

How are the * 

sulphates produced either by the direct combination 

forme . Q ^ su }pi lur j c ac j(j with the proper oxide, or 

by its action on the metals. The latter has been already 
particularly described in the section on Sulphuric acid. 
They are also sometimes formed in nature by the 
action of the air on sulphurets. In this action the 
metal is converted into oxide, and the sulphur into acid, 
which together form the sulphate. Green vitriol is 
sometimes thus formed in soils from sulphuret of iron 
or fooVs gold. 

What is qyp- 770. SULPHATE OF LIME. GYPSUM. 

** m - This is a white, soft mineral occurring 

abundantly in nature. The finer kinds are known as 
alabaster. Finely ground, it is employed extensively 
as a fertilizer of the soil under the name of plaster. 
Plaster of Paris is produced by heating gypsum until 
its water is expelled. The plaster, when pulverized, 
has the property of setting with water, or, in other 
words, forming a hard coherent mass. 

771. Plaster casts — Plaster casts are 

JJow are plas- , _ _ . , n n -. 

ter casts pro- made by reducing burned or powdered 
ducedi gypsum to the consistence of cream, with 



306 SALTS. 

water, and then pouring it into moulds. A coin may 
be copied by pouring such a paste into a small paper box 
containing the coin. Two parts of ordinary ground 
gypsum, heated moderately until vapor ceases to escape, 
and then mixed with one part of water, form a good 
proportion. The heat should not be carried very far 
beyond that of boiling water, or the plaster refuses to 
set. 

772. The hardening of the plaster part 

Wliydoplas- .„ T r . 

ter casts hard- takes place very rapidly. It is owing to 
€n * the re-combination of the material with 

water. The water thus absorbed exists in a solid form 
in the compound, as in other salts. 

773. Aluminated plaster. — Harder and 

What is alu- 

minated plas- better casts, more nearly resembling mar- 
Ur - ble, are made by steeping the burned gyp- 

sum for six hours in strong alum water, and then re- 
heating it at a higher temperature. After being again 
pulverized, it may be used like ordinary plaster, but 
requires more time to harden. 

774. Sulphate of soda. — Glauber's 

Describe sul- ,-,,, . , ., ,, r 

phauo/soda, salt.— This is a white salt forming crys- 
and itsprepa- ta ] s belonging to the third system, such as 

ration. 

are represented in the fig- 
ure. It is used to some extent in medi- 
cine, and in large quantities for the pro- 
duction of carbonate of soda. It is prepared by pour- 
ing oil of vitriol upon common salt. A double decom- 
position takes place between the salt and the water of 
the acid ; hydrochloric acid is formed, which passes off, 
and soda, which remains combined with the sulphuric 



SULPHATES. 307 

acid. It is to be understood that this reaction between 
water and common salt, takes place only when sulphuric 
acid is present. The method of making the experi- 
ment is given in the paragraph on the preparation of 
hydrochloric acid. 

What is said 775. Sulphate of soda may be obtained 
of its crystals? j n cr y S tals by evaporation. These crys- 
tals, like those of many other salts, lose their combined 
water on exposure to the air and become converted 
into a white powder. This change is called efflores- 
cence, and the salt which experiences it is called efflo- 
rescent. In preparing the salt on a large scale, for 
conversion into carbonate of soda, great quantities of 
hydrochloric or muriatic acid are incidentally pro- 
duced. 

What is ml- 7 ?6. Sulphate of baryta.— The sul- 

phate of ba- phate of baryta is a white insoluble sub- 

ryta? How A . / 

prepared? stance, which may be obtained as a pre- 
s? cipitate, by double decomposition of any 

soluble baryta salt with a soluble sulphate. It is a 
mineral of frequent occurrence, known as heavy spar. 
It is used for the adulteration of white lead, in which 
it may be easily detected as a residue, on dissolving 
the white lead in dilute nitric acid. The sulphate of 
lead is another of the few insoluble sulphates. 

777. Alum. — Ordinary alum is a double 

Describe 

alum, and its sulphate of alumina and potassa. Solu- 
preparation. tj ons f tf\ e two sa it s? when mixed, com- 
bine to form the double salt. The sulphate of alu- 
mina required in the process may be obtained by dis- 
solving alumina from common clay by sulphuric acid. 





308 SALTS. 

Or it may be produced by exposing cer- 
tain clays or slates which contain sul- 
phuret of iron to the action of the air. 
Under these circumstances the sulphur 
becomes converted into sulphuric acid, 
which unites with both oxide of iron and alumina. 
From this mixture the protosulphate of iron is sepa- 
rated by crystallization, leaving a solution of sulphate 
of alumina to be used in the preparation of alum. 
What is burnt 778. On heating alum in a crucible or 
alum? pipe-bowl, it swells up into a light porous 

mass and is converted into burnt alum. At §>§ 
the same time it loses its water of crystalliza- 
tion, of which it contains twenty-four molecules 
to each molecule of the double sulphate. 

779. Other alums. — The name alum 
of other is applied to a number of salts of analo- 

gous composition to the common alum al- 
ready described. In one of these, sesquioxide of chro- 
mium, and in another, sesquioxide of iron, takes the 
place of the alumina or sesquioxide of alumina. In 
a third kind of alum oxide of ammonium replaces the 
potassa. All of these alums contain the same number 
of molecules of water of crystallization. They have 
all the same crystalline form, and, if mixed in solu- 
tion will crystallize together. They are, therefore, 
isomorphous salts. Their perfect analogy of composi- 
tion will be best seen by the inspection of their formu- 
lae, given in the Appendix. 

What is said ^80. OTHER SULPHATES. YlTRIOLS. 

of vitriols? Several of the sulphates have received the 



NITRATES. 809 

common name of vitriols. Sulphates of zinc, copper, 
and iron are called respectively white, blue, and green 
vitriol. Green vitriol readily absorbs oxygen from the 
air, and becomes brown, from the accumula- 
tion of peroxide of iron upon its surface. A 
solution of it is changed to a yellowish-red 
color by the oxidizing action of either nitric 
acid or chlorine. A crystal of blue vitriol is 
represented in the figure. The form belongs to the 
fifth system. 

NITRATES. 

How are ni- 781. The nitrates are formed by 

trait* formed? i\ ie action of nitric acid on metals, >r\ 
as already explained, and also by the action of f 
the acid on oxides previously formed. In the 
latter case, the metallic oxide takes the place of 
the water of hydration which always belongs \Jy 
to the acid. They are also produced by double 
decomposition. This latter method is illustrated be- 
low, in the preparation of nitrate of potassa from the 
nitrate of lime. The figure represents a crystal of salt- 
petre. The form belongs to the third system. 

782. Nitrate of lime. — This salt is 

How is nitrate 

of lime pro- of considerable interest, from the fact that 
it is employed in the production of salt- 
petre or nitre. It is formed in the so called, nitre beds. 
by mixing together refuse animal matter with earth and 
lime. In the gradual putrefaction of the animal mat- 
ter which follows, its nitrogen takes oxygen from the 



310 SALTS. 

air, and is converted into nitric acid. The acid then 
combines with the lime to form the nitrate. The salt 
is afterward extracted by water. The formation of 
nitric acid, above mentioned, takes place only in the pre- 
sence of alkaline substances. In their absence the ni- 
trogen passes off, combined with hydrogen, as am- 
monia. Even in the presence of lime, there is reason 
to believe that ammonia is first formed, and its consti- 
tuents afterwards converted into nitric acid and water. 
_ . . , 783. Nitrate of potassa. — Nitre, or 

Explain the m m • 

formation of saltpetre. — This salt is a constituent of 
certain soils, especially in warm climates. 
These soils always contain lime, and are said to be 
never entirely destitute of vegetable or animal matter. 
It is obvious, therefore, that nitrate of potassa may be 
formed in them, as the same salt of lime is formed in 
the nitre beds just described. A small proportion of 
nitric acid exists in the atmosphere, combined with am- 
monia. This, also, may be a source of part of the 
nitric acid of the nitrous soils. Again, it is probable 
that nitric acid is slowly formed from the atmosphere 
by the direct combination of its elements in the porous 
soil. Nitre, on being highly heated, yields a third of 
its oxygen in the form of gas. 

784. Nitre is obtained from nitrous soils 

J I r W is nitre 

obtained from by lixiviation with water and subsequent 
nitrous soils? cryst allization. From nitrate of lime, 
it is produced by double decomposition with carbonate 
of potassa. Carbonate of lime precipitates, while nitrate 
of lime remains in solution. This may be afterward 
poured off, evaporated, and crystallized. 



NITRATES. 311 

„ . 785. Uses of nitre. — Nitre is exten- 

Mention so7iie 

of the uses sively employed by the chemist and in the 
of mut artg ^ ag an oxidizing agent. A few grains 

of it introduced into a solution of green vitriol or sul- 
phate of iron, to which some free sulphuric acid has 
been added, will immediately change its color. The 
sulphuric acid sets nitric acid at liberty, to which the 
oxidation and change of color are to be attributed. 
Nitre, when heated, yields part of its oxygen, as before 
stated. If heated with metals, it converts them into 
oxides. The principal use of nitre is in the manufac- 
ture of gun-powder. 
tt .„ • 786. Nitrate of ammonia. — Laughing 

How are ni- 
trate of am- gas. — Nitrate of ammonia may be prepared 

monia and r . . . ... 

laughing gas from the carbonate by evaporation with 
produced? nitric acidt When heated, the hydrogen 

of the ammonia and an equivalent quantity of the ox- 
ygen of the nitric acid unite to form water, and the 
residue of both passes off as protoxide of nitrogen or 
nitrous oxide. The compound is also called laughing 
gas, from the exhilarating effects which it occasions 
when breathed in considerable quantity. Impurity 
of material or excess of heat occasion the production 
of an impure and deleterious gas. In view of these 
facts, tho preparation and inhalation of laughing gas 
is not to be recommended to the student. 
„ 7 . _, 787. Gun-powder. — Gun-powder is a 

Explain t»e r 

action of the mixture of nitre, charcoal, and sulphur. 
shtuents of 1 ' When ignited, the carbon burns instanta- 
gun-powder. neously, by help of the oxygen of the nitre, 

thus producing a large volume of carbonic acid gas. To 

14 



312 SALTS. 

this gas, together with the nitrogen which is also set at 
liberty at the same moment, the force of the explosion 
is due. The sulphur at the same time combines with 
the potassium of the nitre, and remains with it as a 
sulphuret of potassium. Three equivalents of carbon 
to one of nitre and one of sulphur expresses very 
nearly the composition of gun-powder. It varies, how- 
ever, according to the uses for which it is intended 
and the country in which it is manufactured. From 
tae proportion, by equivalents, the relative weight of 
the constituents can readily be calculated. 

788. Collection of the gases. — For 

How are the 

gases col- the production and collection of the gases 
evolved in the combustion of gun-powder, 
the fuses of ordinary "firecrack- 
ers" may be employed. Several 
of them are to be iguited at the 
same time in an ordinary test- 
tube. The mouth of the latter 
being then brought under a filled 
and inverted vial, the gases are 
collected as fast as they are evolved. 

789. Nitrate of silver. — Nitrate of 

Describe ni- ., 7 , . . i j • 

trate of silver, silver or lunar caustic is employed m 
What are its sur gery , for cauterizing wounds. A solu - 

uses? ° J 7 ° 

tion of the salt in which the oxide has 
been precipitated by ammonia and re-dissolved by a 
slight excess, is extensively employed as an indelible 
ink. The black color comes from oxide of silver and 
finely divided metal precipitated in the cloth. It 
may be removed by soaking in solution of common 




CARBONATES. 813 

salt, and thus converting the silver of the mark into 
chloride of silver. This is soluble in ammonia, and 
may be afterward extracted by that agent. Nitrate 
of silver is also the basis of most dyes for the hair. 
Describe the 790. Other nitrates. — Nitrate of soda 

other nitrates. j g a w hit e salt, found native in South 
America. It is used in the manufacture of nitric acid, 
and, to some extent, as a fertilizer of the soil. The 
remaining nitrates are soluble salts, of colors corres- 
ponding to the solutions of the metals, as already de- 
scribed. The uses of the nitrates of silver and bismuth 
have already been mentioned. 

CARBONATES. 

Describe the 791. Carbonates. — The carbonates are, 

carbonates. f or ^ e m ost part, white or light colored 
salts, of which chalk may serve as an example. The 
carbonate of copper is found native, both as blue and 
green malachite. All of the carbonates, 
excepting those of the alkalies, may be j 
decomposed by heat. The latter are sol- L — 
uble and retain their acid at the highest temperatures. 
The figure represents a crystal of carbonate of lime or 
calc spar. 

792. Preparation. — The insoluble car- 

How are the -i -i i ... 

insoluble car- bonates may be produced by precipitating 
h pa7eT? PT6 ' solutions of the metals or their salts by 
carbonic acid or solutions of the alkaline 
carbonates. In the latter case, a double decomposition 
occurs with exchange of acids and bases. 

14* 



314 



SALTS. 



Wkat is said 
of carbonate 
of potassa ? 



Describe car 
bonate of 
soda. 



793. Carbonate of potassa. — Potash. 
The method of preparing potash and 
pearl ash, from wood ashes, has already 
been considered in the paragraph on Potassa. Saleratus 
is a carbonate containing a large proportion of carbonic 
acid. Its use for " raising" bread and cake is familiar. 
The acid employed with it, sets the carbonic acid gas 
at liberty and thus puffs up the "sponge." 

794. Carbonate of soda. — Soda. — 
Carbonate of soda is commonly known 
under the name of soda. It is a white 

soluble salt, familiar from its use in Seidlitz and soda 
powders. Its carbonic acid is the source of the effer- 
vescence in these preparations. 

795. Carbonate of soda is prepared from 

How is carbo- „ . . 

nate of soda the sulphate of soda. 1 his salt being 
prepared? heated with charcoal is converted into 
sulphide of sodium. On heating the latter with car- 
bonate of lime, a double de- 
composition occurs, and car- 
bonate of soda is produced, 
with sulphide of calcium as 
an incidental product. Both 
parts of the process are com- 
bined in practice. Sulphate 
of soda, chalk, and coal, are heated together in a rever- 
beratory furnace, the carbonate of soda is then dissolved 
out from the fused mass, dried, purified, and subse- 
quently crystallized. The sulphide of calcium would 
dissolve at the same time, and thus defeat the process, 
were it not rendered insoluble by combination with a 
certain quantity of lime. 




CARBONATES. 315 

Describe an- ^96. Another method of manufacturing 

other method, carbonate of soda, consists, essentially, 
in separating sulphur from the sulphate, by means of 
oxide of iron, and substituting carbon in its place. In 
this process also, the materials are heated with charcoal, 
in a reverberatory furnace, and the carbonate afterward 
extracted by water. The impure uncrystallized carbo- 
nate of soda, is known in commerce, as soda ash, and 
is largely employed in the manufacture of hard soap 
and in other processes. 

What is sal ?97. CARBONATE OF AMMONIA. SaL VOL- 

volatile? attle. — The ordinary sal volatile of the 

shops, used as smelling salts, is a carbonate containing 
three equivalents of acid to two of base. It wastes away 
gradually in the air, and passes off in a gaseous form. 
„ . , 798. Preparation. — Sal volatile is pre- 

How is sal 

volatile pre- pared by heating together carbonate of 
pare ' lime and chloride of ammonium. Carbo- 

nate of ammonia immediately passes off, while chloride 
of calcium remains behind. The carbonate is led into 
a cold pipe or chamber, where it takes the solid form. 
The mixture of chalk and sal ammoniac is sometimes 
used as smelling salts. The production of sal volatile 
from the mixture is very gradual if heat is not applied. 
799. The property from which 

How is it i r j 

proved to be the salt receives its name, may 
volatile? be illustrated; by holding in its 

vicinity a rod or roll of paper moistened with 
strong muriatic acid. A dense cloud of sal 
ammoniac is immediately produced in the 
air, from the union of the two vapors. The 




316 



SALTS. 



experiment is more striking, if the sal volatile is wanned 
in a cup or other vessel. This salt is sometimes 
used by bakers for making bread and cakes light and 
spongy. 

800. Carbonate of ltme. — Carbonate 

What is said * 

of carbonate of lime, in the form of chalk, marble, and 
of ime ordinary limestone, is a most abundant 

mineral. Whole mountain, chains consist of the latter 
rock. The shells of shell-fish are principally carbon- 
ate of lime. There is good reason, indeed, to believe 
that all limestones have their origin in accumulations 
of such shells, which have been consolidated in the 
course of ages. 

801. Solubility in carbonic acid. — 
The solubility of carbonate of lime in 
carbonic acid is readily shown, by passing 
a current of the gas through 
water clouded with pulver- 
ized chalk or marble. Other mineral 
substances which form the food of plants 
are dissolved by the same means, and 
then find their way into the roots, to 
subserve the purposes of vegetable life. 

802. Incrustations in boilers. — Car- 

What is said . 

of incrusta- bonate oi lime dissolved in carbonated 
tions in boil- wa t er i s again precipitated on boiling the 
solution. This is owing to the escape of 
the acid. Incrustations in tea-kettles and steam-boilers, 
in limestone districts, owe their origin to the same cause. 
In some cases, the crust is formed of gypsum or other 
earthy matters contained in the water. One method 
of avoiding this inconvenience in steam-boilers, is by 



How is the 
solubility of 
carbonate of 
lime in car- 
bonic acid 
shown ? 







PHOSPHATES. 317 

the addition of a smaller boiler in which the water >s 
first heated and its sediment deposited. 
What are §03. Stalactites. — The masses of car- 

stalactuesl bonate of lime which hang like mineral 
icicles from the roofs of caverns are called stalactites. 
The water that penetrates the soil is the architect of 
these curious forms. Impregnated with carbonic acid 
derived from decaying vegetation, it takes up its load 
of carbonate of lime as it settles through the rock, and 
deposits it again on exposure to the air of the cavern, 
in various and often fantastic shapes. Another portion 
of water, dripping to the floor of the cavern, builds up 
similar forms, called stalagmites, from below. 

804, Artificial marble. — The surface 

How is artifi- 

dot marble o\ wood or stone may be marbled by cov- 
produced? e nn<y it with successive coats milk of lime, 
and allowing each in turn to dry before the next is ap- 
plied. The surface is then smoothed and polished, and 
carbonic acid finally applied by which it is converted 
into marble. The milk of lime is simply a mixture 
of slaked lime and water, and may be so colored as to 
produce a variegated surface. 

PHOSPHATES 
Describe the 805. PHOSPHATES. The phosphates, 

phosphates. w j th the exce ption of those of the alka- 
lies, are, for the most part, white insoluble salts. 
Phosphate of lime may be taken as an ex- 
ample. The white residue which is obtained 
on heating the bones of animals until all the 
animal matter is destroyed and expelled, is principally 
phosphate of lime. 



318 SALTS. 

806. Ordinary phosphoric acid has the 

rl < ftlJ 2 5 ordt~ 

nary phospho- property of combining with and neutrali- 
™<*<*4 te™ 1 - z in£ three equivalents of base, instead of 

ed tribasic f ° l 

one, as is the case with most other acids. 
It is therefore called a tribasic acid. The hyd rated 
acid contains, also, three equivalents of water, and may 
be regarded as a salt in which the water acts the part 
of base. Arsenic acid is similar in this respect, as well 
as in the amount of oxygen which it contains and in 
the salts which it forms with bases. Two other kinds 
of phosphoric acid may be prepared from that above 
mentioned ; the first combines with one, and the second 
with two equivalents of base. 

807. Preparation. — The phosphates of 

How are the ,'-,,,. -, -i i i i 

phosphates the alkalies may be produced by the ac- 
prepared? tion of phosphoric acid on the proper car- 
bonates. The remaining phosphates may be precipi- 
tated by solution of phosphate of soda from solutions 
of the metals or their salts. As in other cases of pre- 
cipitation, there is here a double decomposition with 
exchange of acids and bases. 

808. Superphosphate of lime. — A 

Hcscribe the 

preparation mixture bearing this name, formed by the 
of superphos- ac ti on of dilute sulphuric acid on burned 

pkate oj time. r 

bones, is extensively used as a fertilizer of 
the soil. The sulphuric acid, when added, appropri- 
ates part of the lime of the bones, forming with it 
gypsum ; at the same time, it leaves the phosphoric 
acid which it displaces free to combine with another 
portion of phosphate of lime and thereby to render it 
soluble. The commercial article is a mixture of this 




SILICATES. 319 

soluble substance with the gypsum and animal char- 
coal produced in its formation. Other materials are 
often added, increasing or diminishing, according to 
their nature, its agricultural value. The basis of the 
manufacture is commonly the refuse bone black of 
sugar refineries. 

809. Other phosphates. — T: e phos 

What is said . 

of other phos- phate of soda is used in medicine 
phates? an( j ky t j ie c h em j stj t0 produce 

other phosphates. The phosphate of silver is 
a beautiful yellow precipitate, obtained by pre- 
cipitating salts of silver with phosphate of 
soda or any other salt containing phosphoric acid. 

SILICATES 

What is said 810. The silicates form an exceedingly 
of silicates? large class of salts. They are, for the 
most part, insoluble, and are variously colored. 
Mica and feldspar, two of the constituents 
of granite, may serve as examples. As com- 
ponents of this and other rocks, the silicates 
make up a very considerable portion of the 
mass of the earth. 

811. Preparation. — Most silicates may 

How are sili- . . __ - , . „ . 

catcspre- be artificially formed by fusing together 

pared? quartz sand and the proper oxide. This 

is done in the manufacture of glass, to be hereafter 
described. Silicates may also be formed by precipita- 
ting solutions of metals or their salts by the solution 
of an alkaline silicate. 




320 SALTS. 

81.2. Clay. — Clay is a silicate of alu- 

Wkat i* the J 

composition mina, commonly containing silicate of po- 
ofcay tassa and other materials in small pro- 

portion. The best kaolin or porcelain clay is perfectly 
white, and is nearly pure silicate of alumina. 
How is soluble 813. Soluble glass.— -Soluble glass is 
glass made i made by fusing sand with potassa or soda. 
Its production may be illustrated in a soda bead, by 
-subsequently re-fusing it with addition of sand. As 
the silicic acid combines with the soda carbonic 
acid is expelled, as will be evident from an efferves- 
cence on the surface of the bead. Soluble glass is 
sometimes used as a sort of varnish for rendering wood 
fire proof. 

814. Window glass. — Common window 

Describe the 

manufacture glass is a silicate of lime and soda. To 

of ia l sT d ^ w form il > chalk > soda > q uartz sand and old 

glass are fused together until the mass be- 
comes fluid. The molten glass is then blown, by 
means of an iron tube, as soap bubbles are blown 
with a pipe. The first form of the bubble is 
that represented in the figure. The glass blower 
next contrives to lengthen out the bubble, as he 
blows it, to a larger size, and finally to blow out 
the end by a strong blast from his lungs. It 
is then trimmed with a pair of shears, and the 
other end cracked off by winding round it a thread 
of red hot glass. Such a thread is readily produced 
by dipping an iron rod into the pot of molten glass, and 
then withdrawing it. The bubble of glass is thus 



GLASS. 



321 




brought to the form of a cylinder, such as is 
represented in the figure. The cylinder is 
then cracked longitudinally, by letting a drop 
of water run down its length, and following it 
by a hot iron. It is subsequently reheated, 
opened, and flattened out into a sheet, which 
is then cut into panes of smaller size, if required. 
How are glass 815. Glass tubes. — To make a glass 
tubea made? tube, a bulb is first blown, such as is repre- 
sented on the previous page. An assistant then at- 
taches his tube to the hot bulb at the opposite side, 
and moves backward. The glass is thus drawn out 
as if it were wax, and the cavity within it is elongated 
to a smooth and perfect bore. 

816. Glass bottles — Bottles and a 
great variety of other objects of glass are 
made by the enlargement of similar bulbs within a 
mould of the required shape. Bottle glass is usually 
made of cheaper and less pure materials than window 
glass, and contains, in addition to the materials before 
mentioned, alumina and oxides of iron and manganese. 
It owes its green color to the protoxide of iron. 
Glass mir- 817. Glass mirrors, — Plate glass, such 

rors - as is used for mirrors, instead of being 

blown, is cast in metallic tables of the required shape, 
and then rolled out and polished. 

Whatiscrys- 818. Crystal glass.— This name is 
talqlass? given to a highly brilliant glass contain- 
ing potassa and litharge as bases. It is used for prisms, 

tenses, lustres, and the finer qualities of cut glass ware. 

14* 



322 



SALTS. 



With the addition of borax, it is also employed for im- 
itations of precious stones. 

What is ena- 819. Enamel. — Enamel is an opaque 

mel? glass, produced by the addition of some 

material which does not dissolve in the fused mass. 
Binoxide of tin is the material commonly employed. 
Various tints may be imparted to enamel, as to ordi- 
nary glass, by the addition of small quantities of me- 
tallic oxides. A thin surface of enamel is often baked 
on to a metallic surface, as in the case of watch dials 
and various objects of jewelry. 

How is glass 820. Colored glass. — Glass is colored 
colored? an( j stained by the addition of various me- 

tallic oxides. The peculiar coloring effects of these 
substances have already been mentioned, in the sec- 
tion on Oxides. 

EARTHENWARE. 



What is the 821. Clay is the basis of all earthenware, 

basis of all from the finest porcelain to the coarsest 

earthenware " 

Howisporce- brick. Being first fashioned by moulds or 

lain made? Qther intQ the ^ ^/^ 



proper form, it is dried, baked, and 
subsequently glazed to render it 
impervious to water. In the man- 
ufacture of porcelain glazing is not 
essential. Sand and chalk are ad- 
ded to the original material, and 
the heat is carried so high as to 
bring the whole mass into a semi- 
vitreous condition. This is also 
the case in certain kinds of stone- 




BORATES. 323 

ware. Porcelain is, however, commonly glazed to add 

to its beauty. 

^ -i ,t 8522. Glazing. — Earthenware after its 

JJescrioe the 

process of first baking is porous, and therefore unfit 
glazing. ^ mogt useg ^ ^^ it - g intended. It 

is subsequently covered with a thin paste formed of 
the constituents of glass. Being then subjcted a 
second time to the heat of the furnace, a thin glass 
or glaze is formed upon the surface. The glazing 
of certain wares is effected by exposure at a high 
temperature to vapors of common salt. A double de- 
composition ensues with the oxide of iron which the 
ware contains, by which soda is formed. This imme- 
diately fuses with the silica and other materials to form 
the glaze. The chloride of iron which is formed at 
the same time passes off as vapor. A paste of pounded 
feldspar and quartz, to which borax is sometimes added, 
is employed in glazing porcelain. 

823. Porcelain painting. — Metallic 
of porcelain oxides form the basis of the pigments used 
painting, j n p a j_ n tiiig upon porcelain. The color- 
ing effect of the different pigments is mentioned in the 
chapter on metallic oxides. The patterns on ordinary 
earthenware are first printed on paper, and then trans- 
ferred, by pressure, to the unglazed ware. The paper 
is afterwards removed by a wet sponge. 

BORATE& 

What is 824. Borax. — Borax is the only impor- 

borax? | an t sa lt among the compounds of boracic 



324 s/ilts. 

acid. The salt contains two atoms of acid to 
one of base, and is therefore a biborate. It is a 




white soluble salt, which swells up when heat- 
ed, in consequence of the escape of its water 
of crystallization. 

How is borax 825. Preparation. — Borax is found in 
prepared? solution in the water of certain shallow 
lakes in India. It remains as an incrustation in the 
beds of these lakes when they dry up in summer. It 
is also prepared by the action of a solution of boracic 
acid on carbonate of soda. 

What is said 826. Borax glass.— The light spongy 

of borax glass? mass which is produced on heating borax, 
may be melted down by greater heat and converted into 
borax glass. This glass has the property of dissolving 
metallic oxides, and receiving from them peculiar colors, 
as described in a former paragraph. The chemist often 
determines the metal which a salt or oxide contains, 
by the color which it thus imparts to glass. The 
method of making the experiment has already been 
given. 

827. Soldering, welding, etc. — Borax 

WJiy is borax . i i • i i • i 

employed in is employed in soldering metals, to keep 
soldering? ^ meta ui c surfaces clean. It does this 
by dissolving the coating of oxide which forms upon 
them, and forming with it a glass which is fluid at a 
high temperature, and easily pushed aside by the 
melted solder. Its use in welding iron depends on the 
same property. Borax is also used, to some extent, in 
medicine. It is also a constituent of the plass called 



CHROMATES. 



325 




jewellers paste, which is used in producing imitations 
of precious stones. 

CHROMATES. 
828. Chrome yellow. — To prepare this 

How is chrome . . , 

yellow pre- pigment, a solution 01 the commercial 
pared? bichromate of potassa is added to a solution 

of sugar of lead. A double decomposition ensues : the 
result of which is the production of a beautiful 
yellow precipitate, known as chrome yelloio. 
The precipitate is a chromate of lead. The 
bichromate of potassa used in the experiment, is 
made from the mineral chrome iron, which has 
been mentioned in a previous chapter. The acid itself, 
which is without practical applications, may be made 
from the salt. It contains, like sulphuric acid, three 
atoms of oxygen. 
tt . * 829. Chrome orange. — Chrome yellow 

How is chrome J 

yellow con- ma y be converted into chrome orange, by 

verted into 

chrome digestion with carbonate of potassa. Cloth 

orange. dyed yellow by dipping it alternately into 

a solution of bichromate of potassa and sugar of lead, is 
instantaneously changed to orange by immersion in 
boiling milk of lime. This action of the lime, as well 
as that of carbonate of potassa, depends upon its ab- 
stracting a certain portion of the chromic acid, leav- 
ing thereby a chromate of lead of different composi- 
tion and color. 



326 SALTS. 

830. Chrome green. — On adding sul- 

Dcscribe the . ° 

preparation phuric acid and a lew drops of alcohol to a 
o/ oxide of solution of bichromate of potassa, the solu- 

cnromium. r 7 

tion is immediately changed from red to 
green. The alcohol has taken oxygen from the chro- 
mic acid, and converted it into oxide, which remains 
in solution, as a soluble sulphate. Part of the sulphu- 
ric acid has at the same time combined with the potassa, 
to form sulphate of potassa. It is to the presence of 
the sulphate of chromium in solution that the color of 
the liquid is due. By adding an alkali to the solution, 
a green precipitate of the hydrated oxide is produced. 
This oxide forms a kind of " chrome green." App. 830. 

MANGAKATES. 
TTr7 . ■ 831. Chameleon mineral. — By fusion 

XVtiat is cha~ 

meleon miner- with nitre, the black oxide of manganese 
a l * may be still further oxidized, and converted 

into an acid. The new acid at the same time com- 
bines with the potassa of the nitre to form manganate 
of potassa. This salt has been called chameleon min- 
eral, from the spontaneous change of color which 
takes place in its solutions. 

832. Preparation. — The experiment 

How is chame- _ . . 

Uon mineral may be made by filling a pipe stem with 
prepared? a m j xture f t h e materials, and thrusting it 
into burning coals. It may be made on a still smaller 
scale before the blow-pipe, using a broken pipe-bowl to 
support the materials. The compound dissolves in 
water, forming a green solution, which on standing 
is gradually changed to a beautiful red. 



the daguerreotype. 327 

833. Explanation. — The addition of a 

. action of ml- few drops of sulphuric acid, produces the 

phunc acid above-mentioned change instantaneously. 

upon it ° J 

This acid combines with the potassa, 
setting the manganic acid at liberty. One portion of 
manganic acid then appropriates part of the oxygen of 
the other part, and converts itself into hypermanganic 
acid, which still remains combined with potassa, im- 
parting the red color to the solution. The deoxydized 
portion of the acid precipitates, at the same time, as bin- 
per oxide. The remaining manganates are not of especial 
interest or importance. 



THE DAGUERREOTYPE. 
„ _ . T 834. The daguerreotype. — The da- 

Explain the 

daguerreotype guerreotype may be regarded as a painting 
briefly. ^ n mercury, upon a silver surface. The 

employment of mercury is preceded by what may be 
called an invisible painting upon the silver. This is ac- 
complished, like the production of an image in a mirror, 
by mere presentation of the picture, or other object 
to be copied, before the prepared plate. The mercury, 
afterward used in the form of vapor, adheres to the 
plate, and forms its white amalgam, just in proportion 
to the lights and shades of the previous image thrown 
upon the plate. 

Describe the §35. The DAGUERREOTYPE PROCESS. 

process of ta- j n or( j er to prepare the plate for what has 

king daquer- -,,-,-, • • -i i 

reotypes. above been called the invisible painting, it 

is exposed to vapors of iodine, and thereby covered 



328 s\lts. 

with a coating of iodide of silver.* A picture or face 
to be copied being presented before the prepared plate, 
the light which proceeds from it acts chemically 
Upon the iodide of silver. It decomposes it, to a 
certain extent, and separates the iodine, thus open- 
ing the way for the mercurial vapor which is afterward 
to be employed. The light has this effect just in pro- 
portion to its intensity. That which proceeds from the 
lighter portions of the face, or dress, has most eifect ; 
that from the black portions, none at all, and that from 
the intermediate shades, an eifect in exact proportion 
to their brightness. When the plate is afterward ex- 
posed to the action of the mercurial vapors, they find 
their way to the silver surface and paint it white, just 
in proportion as this chemical effect upon the iodine 
has been produced, and the way has been opened for 
their admission. The darker portions of the plate are 
pure silver. They appear dark in contrast with the 
white amalgam.f 

836. Use of the lens. — In taking da- 

What is the i ' " ' - i t i i 

object of the guerreotypes, a lens is placed between the 
lens ' object to be copied and the plate, in order 

that an image may be formed on the silver surface. Such 
an image is analogous to that formed on the retina of the 
eve. The image is commonly made smaller than the 
object. Where this is the case, the rays are used in a 
concentrated condition, and their effect is proportionally 
increased. 



* Bromide and chloride ot iodine are employed to give additional 
sensitiveness to the plate. The iodide is thus made to contain a por- 
tion of bromide and chloride of silver. 

f The art of taking portraits from the life by the Daguerreotpe pro- 
cess, was invented by Dr. J W. Draper, of the N. Y. University. 



PHOTOGRAPHS. 329 

837. Chemical action of light. — The 

What is said 

of thechemi- chemical action of light, on which the 
Uql™i %01 What production of daguerreotypes depends, is 
rays possess one f the most interesting and remarkable 

this power / . 

of chemical phenomena. The rays of 
the sun are so subtle that they p&ss through solid crys- 
tal and leave no trace of their passage. Yet with them 
comes a power that can overcome the strongest chemical 
affinities, and resolve the compounds which it has pro- 
duced into their original elements. This power resides 
in what are called the chemical, actinic, or tithonic rays. 
These are mingled, under ordinary circumstances, with 
those of light, but are capable of separation by certain 
media. 

What are pho- 838. Photographs. — Pictures produced 
tographs? through the agency of light, whether upon 
silver or paper, are, properly, photographs or light pic- 
tures ; the name, however, is especially appropriated 
to the latter. For the purpose of illustration, a method 
of producing negative pictures, as they are called, will 
be here given. 

How is sensi- 839 - The sensitive paper required in 

tive paper the process, is prepared by floating a slip of 

prepared? . ~ . . 

letter-paper tor two or three minutes upon 
salt water ; and then for double the time, with the same 
side down, on a solution of nitrate of silver. Chlo- 
ride of silver forms within the fibres, and renders the 
paper sensitive to light. After each immersion, the slip 
should be dried off by blotting paper. When finished, it 
should be immediately laid away between the leaves 
o> \ book, for protection against the light. 



330 SALTS. 

What effect 84 °* SUCh Paper ' if Pla0ed ^ dkeCt 

has direct sun- sun light, becomes violet and then dark 

SffiT^- brown il1 the course of a few minutes. 
P er ? The change is owing to the partial decom- 

position of the chloride of silver. A new substance, 
of darker color, is then produced ; whether a lower 
chloride of different shade, or a mixture of metal and 
chloride, or a compound of oxide and chloride, is not 
very certainly known. 

841. If a cross or other device cut 

Bow may cop- 
ies be pro- from dark paper is pressed down upon 

melts^of sen- sensitive paper, by means of a glass plate, 
sitive paper? an d be left to cover it during the exposure 
to light, the paper will be pro- 
tected beneath it, and an exact 
copy of the device thus ob- 
tained. The most delicate lace 
may be copied by the same method. In reproducing 
engravings by this means, they must be previously 
rendered translucent, so that the imprinted portions will 
allow the light to pass. This may be accomplished by 
waxing them, with the help of a hot iron, or by simple 
oiling. The dark parts of the engraving appear light, 
and the light portions dark, in the picture. By copying 
the copy, a true representation of the original device, 
called a " positive picture," is obtained. Both the " pos- 
itive" and " negative" are soon destroyed by the action 
of light upon the whole sensitive surface. But the 
means exist for rendering them entirely permanent in 
any exposure 



HXY 



COUNTERFEITING. 331 

842. The silver solutions. — To prepare 

How is the sil- 
ver solution the silver solution, above required, put a 

prepay three cent piece into a test-tube, having a 

diameter a little larger than the coin itself. Then fill the 
tube to the depth of an inch with a mixture of equal 
parts of nitric acid and water. The solution of the coin 
commences immediately. When it is completed, fill 
up the tube with water, mix well by shaking, and the 
solution is ready for use. For the same quantity of 
salt solution, enough common salt to fill about two- 
thirds of an inch of the tube may be used. 

843. Anastatic printing. — This name 

Describe 

briefly the is given to a process by which any kind 
astatic print' °f Panted matter may itself be converted 
in 9 * into a plate from which new copies may be 

printed. It consists, essentially, in the transfer of the 
letters or other design, to zinc, by pressure, the paper 
having been previously moistened by dilute acid. 
The oil of the ink remains, and the paper is re- 
moved. The zinc plate is then used like an ordi- 
nary lithographic stone. When the inked roller is 
passed over it, the ink only adheres to the design, from 
which an impression may then be taken by the ordi- 
nary process. 

What issaidof 844 Counterfeiting.— Bank notes may 
counterfeiting ^ e counterfeited by either of the above 

by the above J 

process? processes. Great apprehension has been 

felt lest they should render the use of paper money en- 
tirely insecure. An effectual means of protection 
against such counterfeiting has recently been devised.* 

* Seropyan'a patent. 



332 SALTS 

Copying by the anastatic process, obviously depends 
upon the absence of oil from the back ground of the 
picture. The employment of an oil tint, instead of 
blank paper, for the back ground, is therefore a perfect 
security against it. Counterfeiting by the photographic 
process depends on the fact that the light which falls 
on a picture is intercepted by the dark letters. If they 
are printed in a transparent blue, the chemical rays 
are permitted to pass through the printed as well as the 
imprinted portions. A copy with the contrasts of the 
original picture is thereby rendered impossible. By 
printing with blue ink, on a back ground of some other 
color, both of the securities against counterfeiting 
above mentioned are combined. 



CHEMICAL ANALYSIS. 
845. Direct method. — In the process 

Describe anal- . . * . 

ysis by sol- of analysis, advantage is taken of the dis- 
vents. tinguishing properties of different sub- 

stances to effect their detection and separation. They 
may sometimes be separated by the employment of a 
solvent which acts upon one and leaves the other un- 
dissolved. The separation of silver from gold in the 
process of assaying is a case in point. 
Describe di- 846. A more common method is to bring 

rect analysis ^ e w hole substance into solution, and 

by precipita- . . 

Hon. afterward separately to precipitate its sev- 

eral constituents by agents which have no effect upon 
the rest. The separation of alumina from lime may 
serve as an example. A mixture of the two being dis- 



CHEMICAL ANALYSIS. 333 

solved in acid, the former may be precipitated by am- 
monia. The latter remains in solution and may be 
afterward removed by some other agent. 

847. Indirect methods. — Indirect me- 

Illustrate the . 

indirect meth- thods oi analysis are much more frequently 
od ' employed than either of the above. The 

detection of silver in a copper alloy may serve as an 
example. The alloy being first dissolved, hydrochloric 
acid is added to the solution, as a test. The appearance 
of a white insoluble curd, is taken as conclusive evi- 
dence of the presence of silver. No other metal of an 
alloy ever combines with the chlorine of hydrochloric 
acid to form such a precipitate. The evidence is quite 
as satisfactory to the chemist as that which would be 
obtained by the separation of the silver in the metallic 
form. 

848. Neither is separation necessary in 

How is the . 

weight cahu- order to ascertain the exact weight of the 
metal which has been precipitated. Ad- 
vantage is here taken of the well-established law of 
combination by definite proportions. The chloride of 
silver produced in the experiment, is invariably of the 
same proportional composition. It is made up of an 
atom of silver to every atom of chlorine. Its weight 
being ascertained by the balance, the amount of silver 
which it contains may be calculated with absolute pre- 
cision, by help of the table of atomic weights. This 
weight being compared with that of the original alloy, 
gives, by a simple calculation, the per centage propor- 
tion of silver which the alloy contains. The nature and 
quantity of other constituents, whethel of compounds 



334 CHEMICAL ANALYSIS. 

or mixtures, is determined by processes analogous to 
those which have above been described. 

849. Separation into groups. — In the 
ration into' analysis of substances containing many con- 
groups effect- stituents, a separation into groups precedes 

ed ? 

the isolation of the individual constituents. 
This is eifected by the use of certain agents in suc- 
cession, which have the property of precipitating whole 
groups. These being again dissolved, are commonly 
subdivided into smaller groups by similar means. The 
detection and separation of the individual constituents 
is finally accomplished by means already indicated. 
Some general idea of the process of inorganic analysis 
may be obtained from the foregoing. Particulars upon 
this subject must be sought in works on analytical 
chemistry. 



335 



PART IV.— ORGANIC CHEMISTRY. 



CHAPTER L— GENERAL VIEWS. 

850. Definition. — Organic chemistry is 

Of what does .. . . 

organic chem- that division oi the science which treats 
mtry treat? of substances of animal or vegetable ori- 
gin. Starch, wood, gums, and resins ; the juices, colo- 
ring matters, and fragrant principles of plants ; the 
blood and flesh of animals ; all come under its conside- 
ration. The process of germination, in which the 
plant first comes to be a living thing ; the processes of 
decay and putrefaction, in which it returns again to the 
earth and atmosphere, are also to be treated under this 
division of the subject. Most organic forms of matter 
experience peculiar changes, and are converted into 
new substances by chemical means. The products of 
such transformations belong also to organic chemistry. * 

851. Variety of organic matter. — 

Illustrate the . n . . 

variety of or- The variety oi organic matter is almost 
game matter. w jthout limit. Every color of every dye, 
every flavor of every sweet or bitter herb, every gum, 



* Carbonic -acid, water, bone ash, and some other substances, are ex- 
ceptions to the above rule, and are commonly treated under the head 
of inorganic chemistry. Though often produced from animal and 
vegetable substances, they also exist, ready formed, in nature, or may 
be readily made from inorganic or mineral matter. 

15 



336 ORGANIC CHEMISTRY. 

and every resin, is a distinct organic substance. In 
the animal body, also, there is scarcely less variety. 
The fluids which dissolve the food, the blood which 
distributes it throughout the body, the color which tints 
the skin and hair, and the milk which nourishes the 
young, are a few of the substances which it includes. 
852. Materials of vegetable growth. 

What arc the *«..-- . ,, , .. 

materials of With the exception of the small proportion 
vegetable f m i nera j ma tter which is derived from 

(jiowthf 

the earth, the materials out of which all 
animal and vegetable matter is formed are but few in 
number. Carbonic acid, ammonia, and water, are all. 
These are partly obtained from the air, and partly from 
the earth. Carbon, hydrogen, oxygen, and nitrogen, 
are the four elements which enter into their compo- 
sition. 

What is e- ®^* CONVERSION OF THE MATERIALS.— 

markable in A vital force slumbers within the seed, 

the new ioro~ 

perties which which in germination wakes to life. Call- 
result ? j n g tQ j ts a j^ foe light and warmth of the 

sun, it weaves, as it were, out of the scanty mate- 
rials which have been mentioned, all of the varied 
forms of vegetable matter. Among the materials, one 
is a tasteless solid ; the rest are tasteless gases. Yet 
sweet, sour and bitter flavors result from their combi- 
nation, with all the other boundless variety of the or- 
ganic world. 

854. Similarity of composition. — Yet 
stanctstfsim- more remarkable than the limited number 
ilarity of com- Q f e i emen t s from which so great a varietv 

position with 7 ^ . 

different pro- of organic substances is formed, is the 
p€rtte9 ' similarity of composition in many sub- 



GENERAL VIEWS. 337 

stances which are yet so widely different m their pro- 
perties. Vinegar differs from alcohol, for example, in 
containing a little more oxygen and a little less hydro- 
gen, while the proportion of carbon in each is the same. 
Ether, also, contains the same amount of carbon as the 
alcohol from which it is formed, with a little less hydro- 
gen and oxygen. Yet these substances are all widely 
different in their properties. 

Mention some ^^5. IDENTITY OF COMPOSITION. Most 

tubstane s remarkable of all, and at first view incred- 

w hick are aif- 1 

ferent in pro- ible, is the fact that many organic sub- 
^enticalin stances which are as widely different in 
composition. properties as any which have been named, 
are still precisely the same in their composition ; not 
alone containing the same elements, but containing 
them in pi ecisely the same proportion. The most careful 
chemical investigation finds no difference of composition 
in wood, gum, and starch. The sugar which sweet 
milk furnishes, and the acid which exists in the sour 
contain identically the same proportions of the same 
constituents. The oils of turpentine, lemon and pepper, 
so different in their taste, contain an equal quantity of 
carbon and hydrogen, without the addition of any 
third substance to either to account for the difference. 
Chemical investigation has thus brought us to results as 
strange as the dream of the alchemist, who believed 
that lead might be converted into silver, and copper 
into gold. All such substances, possessing the same 
composition with different properties, are called iso- 
meric bodies — a term signifying their similarity of com- 
position. 

15 



338 ORGANIC CHEMISTRY. 

856. Arrangement of atoms. — At a loss 

How are the 

above farts ac- for any other way of accounting for such 
* for. difference of properties, we are compelled 
to believe that it is because of difference of atomic 
arrangement. We have seen, in the case of iodide 
of mercury, mentioned in a former chapter, that a 
mere touch which produces motion and re-arrange- 
ment of its atoms in smaller groups, at the same time 
changes the color of the compound from yellow to red. 
Now the molecule of lactic acid, although containing 
the same relative proportion of all of its constituents, 
is smaller than the molecule of sugar of milk. It con- 
tains six atoms of carbon, six of hydrogen, and six of 
oxygen. The molecule of sugar of milk contains 
twelve of each, and can therefore furnish material to 
make two of acid, as it does in the souring of milk. 
And we may suppose that the change from sweet to 
sour is owing to this subdivision of the molecules. 

857. There are other cases of identical 

How is diver- . . . . t . ^.^ 

sity of prop- composition, in which there is no dinerence 
erties ac- wnatever in the size of the molecule, or the 

counted j or * 

when there is number of atoms which enter into its com- 

txo difference 

of composi- position. This is the case with the oils of 
honor size? turpentine, lemon, and pepper, and perhaps 
with wood, starch, and sugar. The molecules of each 
are composed, not alone of the same proportion of the 
elements which enter into its composition, but, as there 
is reason to believe, of the same number of atoms of 
each. We are therefore compelled to look for the differ- 
ence which shall account for their peculiar property, in 
a different arrangement of atoms inside of the mole- 



GENERAL VIEWS. 339 

cules themselves. A more satisfactory idea of this sub- 
ject can be obtained after reading what follows, on the 
subject of organic radicals. 

Give an in- 858. Substitution. — A still more re- 

stance of sub- ma rkable evidence of the influence of ar- 

stitution that 

does not affect rangement or grouping of atoms, remains 
proper tQ ^ e mentioned. The internal arrange- 

ment of a molecule remaining the same, it seems to 
matter little, in many cases, of what it is composed 
Hydrogen may even be replaced by chlorine, a body 
as widely different from it as anything which nature 
affords. By this means, ordinary acetic acid is con- 
verted into chloracetic acid, a body remarkably anal- 
ogous in its properties to the acid from which it is 
formed. From this, again, by withdrawing the chlo- 
rine and restoring the hydrogen, the original acetic acid 
is reproduced. 

859 Types. — The last example will 

Wliat is said 

of the doctrine serve as an illustration 01 the doctrine of 
fubsitutions f chemical types and substitution, which cer- 
tain chemists have endeavored to extend to 
all organic bodies. It has been maintained that the 
properties of these bodies depend solely upon arrange- 
ment, without any regard to the nature of the ele- 
ments combined. The fact is, that while there are 
many cases of such substitution without essential 
change of properties, it is always attended by more or 
less modification of the original substance. The 
properties of a compound are therefore to be regarded 
as depending neither upon the nature or arrangement 
of atoms alone, but upon both causes combined. The 






340 ORGANIC CHEMISTRY. 

type, is the group which remains permanent, while the 
individual atoms which compose it are changed. 

860. Compound radicals. — Many or- 

llhistrate the . . J 

subject of com- game bodies, although compounds, com- 
P c °cd s nd mdl ' P ort themselves as if they were elementary 
substances. Some of these are, as it were, 
metals ; forming oxides, chlorides, and salts, like the 
true metals, which have already been considered. 
Others correspond more nearly to the metalloids. Each 
being organic, and like a metalloid, the root of a whole 
series of compounds is called an organic radical. The 
term radical is sometimes applied, for similar reasons, to 
chlorine, bromine, and other elementary substances. 
As the organic substances above referred to are com- 
posed of different elements, they are called compound 
radicals. 

861. Illustration. — A molecule of or- 

Give an exam- . - 

pie of acom- dinary ether is composed of four atoms of 
poundradical. car k orij g ve f hydrogen, and one of oxy- 
gen. But the carbon and hydrogen atoms are grouped 
together, forming a compound radical called ethyle, 
with which the oxygen is then com- *fv^ 

bined to form ether or oxide of ethyle. ^^s^£^a% 
Alcohol, as illustrated in the figure, is ^^^^M^/nN 
the hydrated oxide of this radical. Al- w w w 
dehyde, a substance to be hereafter more particularly 
described, has the same composition as alcohol, with 
the exception that two atoms of hydrogen have been 
removed from the radical. Acetic acid is formrd from 
aldehyde by the re-placement of the removed hydrogen 
by the same number of atoms of oxygen. Ethyle itself 
may be prepared indirectly from the oxide, as potassium 



HOMOLOGOUS SERIES. 341 

is obtained from potassa or oxide of potassium, although 
by a different process. 

What were the 862. It is but a few years since the 
grounds of be- m ethod of producing ethyle was discovered, 

L%€T \YL Zfi€ €£~ 

isience of but chemists believed in its existence al- 
mtfto *itsdis- most as confidently before, as now. They 
coveryi reasoned that ether, which possesses the 

properties of an oxide, must have its radical, as Sir 
Humphrey Davy reasoned that potassa, soda and lime, 
must each contain its metal. 

863. Homologous series. — Certain of 

What are ho- * . 

mologous these compound radicals sustain to each 

senes? other a curious numerical relation. They 

form a series in arithmetical progression, differing from 
each other in composition, by a common difference. 
Two atoms of carbon with two of hydrogen forms the 
common difference of the series referred to. Methyl, 
the radical of wood spirit, begins the list with two atoms 
of carbon and three of hydrogen. Ethyle follows — its 
composition being expressed by the addition of the 
common difference to the last. Margaryl, a radical 
contained in certain fats, is the seventeenth member of 
the series. Each of these radicals has, like ethyle, its 
own oxide or ether, its hydrated oxide or alcohol : also 
its aldehyde and its acid. A series of radicals, ethers, 
alcohols, aldehydes and acids, each in arithmetical pro- 
gression, is thus produced. Such series are called Ao- 
mologous. 

864. Production. — There are many gaps 

IToic arc the . ■.■ \ 

different fnem- in most of the series, but the law of their 
erspro uce , progression is so well established, that no 






342 ORGANIC CHEMISTRY. 

doubt can exist as to the probable production of the 
missing members. The most complete of the series is 
given in the Appendix. Several of its more simple 
members may be produced by the action of nitric acid 
upon those higher in the scale. The acid has the effect 
of burning out part of their carbon and hydrogen, and 
thus reducing the relative proportion of these constitu- 
ents. 

865. Progression of properties.- 

What is said 

of the relation There is also a similar progression of pro- 
TertielY™' P erties in the series. The earlier mem- 
bers of the alcohol series are highly vol- 
atile liquids ; the later are solids at ordinary tempera- 
tures. Each increase of the relative properties of car- 
bon and hydrogen produces a substance which is more 
fixed. In other words, the boiling point is higher for 
each successive member. The difference for each is 
about 34° F. The density of the vapors increases by 
a similar law. It is thus possible to predict, with accu- 
racy, the boiling point and density of vapor in members 
of the series which have not yet been discovered. 

866. Radicals not isolated. — The 

Have all or- _ r . . 1 . , , 

ganic radicals larger part of the organic radicals have not 
been isolated? y et been isolated. They are only known 
in their compounds, and the belief in their existence 
rests on the reasoning which has been given in a previ- 
ous paragraph. This is regarded by chemists as abun- 
dantly sufficient for giving them names and places 
among chemical compounds. It is still, however, to 
be borne in mind, that the reasoning is not of the nature 
of absolute demonstration. 



SUBSTITUTIONS. 343 

Mention some 867 * SUBSTITUTION COMPOUNDS.— It Was 

instances of stated, iri a previous paragraph, that there 

the substit"- ~ . r . . 

tionofradi- are many cases oi substitution of the ele- 
cals ' ments for each other without material 

change of properties. Certain cases of substitution of 
organic radicals for the elements remain to be men- 
tioned. Theoretically considered, they form, perhaps, 
the most important discoveries which have for years 
been made in organic chemistry. Ammonia, as the 
student is already informed, is a volatile base whose 
molecules consists of one atom of nitrogen and three 
atoms of hydrogen. For one of these atoms of hydro- 
gen, a molecule of the radical ethyle may be substituted, 
without very materially affecting its properties. The 
new ammonia thus formed is, like the first, a volatile 
base resembling the first so nearly in odor that it must 
have been repeatedly mistaken for it when accidentally 
produced. It is, however, a liquid at ordinary temper- 
atures. This body has received the name of ethyla- 
mine. Methylamine is another body of the same series, 
produced by the replacement of two of the atoms of am- 
monia by the radical ethyl. Triethylamine is a third. 
By a similar substitution of hydrogen in ammonia by 
the radical methyl, another series is produced. Other 
radicals yield other series. 

868. Other substitutions. — There are 

^Atcntxon otJiet* 

cases of sub- other bodies which result from the substi- 
stitntion. tution of different radicals or the metal pla- 

tinum for the different atoms of hydrogen. Substitu- 
tions may even exist in the substituting radicals. All 
of these bodies retain the type of ammonia, and ail of 



344 ORGANIC CHEMISTY. 

them have basic properties. Many of them are strikingly 
similar to ammonia in odor and other properties. These 
substitution compounds afford still further evidence of 
the influence of arrangement of atoms and molecules 
in determining the character of chemical compounds. 
Many of these bodies differ very widely in their com- 
position, and are yet closely allied in their properties. 
The methods of producing the substitutions above 
mentioned, are not of interest to the general student. 
A general notion of substitutions may be obtained from 
the double decompositions with which the student is 
already familiar. 



ORGANIC CHEMISTRY. 345 



CHAPTER It. 



VEGETABLE CHEMISTRY. 

What is said ^^* Germination. — Before the process- 
of germination es of transformation of the materials of the 

and the chan- 
ges which at- earth and atmosphere into the innume- 
tend u i rabIe p ro( i uc ts of the vegetable world can 

commence, a rudimental plant must be developed from 
the seed. The seed itself contains the 
materials for its production. These are 
principally starch, and gluten,* or the other 
substances analogous to each, which are 
hereafter described. The first stage in 
the process is the absorption of moisture 
and oxygen from the air, and the conse- 
quent production of diastase.^ This sub- 
stance has the remarkable property of con- 
verting starch into sugar, and rendering soluble all of 
the remaining gluten of the seed. By the appropria- 
tion of these materials, which have been stored up for 
it in the seed, the germ is developed into a perfect 
plant. It lets down its root into the soil in search of 

* Gluten is the stringy substance which remains on removing the 
starch from dough by long continued kneading. It is further described 
in a subsequent paragraph. 

f Diastase is an oxydized gluten which is always produced from 
gluten in germination. 

15* 




346 



ORGANIC CHEMISTRY. 



mineral food, and lifts its leaves into the atmosphere, 
from which it is to derive its principal nourishment. At 
this point the true vegetative process commences. 

. _ 870. Vegetable nutrition. — Every 

What is the J 

office of leaves leaf is a net to catch the fertilizing con- 
stituents of the air and appropriate them 
to the uses of the plant. It drinks them in through its 
countless pores, while the root supplies the remaining 
material and sends it upward in the rising sap. All of 
these materials meet in the leaf, which is the labora- 
tory in which their conversion into vegetable matter is 
to be accomplished. The light and heat of the sun 
co-operate with the vital forces of the plant in the 
transformation which succeeds. 

871. Whatever proportion of carbonic 

What gas is- ' 

evolved from acid and water may be employed as the 
plants? raw ma terial, ^ is obvious, by comparison 

of their composition with that of vegetable substances, 
as hereafter given, that the oxygen is furnished in 
larger quantity than is required. Water alone yields 
a sufficient supply of this element, and more than 
enough for most substances that are to be formed. As 
the process of transformation proceeds, this gas is there- 
fore constantly thrown off into the air. It is the refuse 
of the manufacture. Inasmuch as the evolution takes 
place from the leaf and other green parts of the plant, 
it is reasonable to suppose that this is the point where 
the process of transformation is principally conducted. 
The gum, sugar, or other materials produced, are dis- 
solved in the descending sap, and transformed into 
other products, in the course of their circulation. 



OFFICE OF THE ROOT. 



347 



How may the 
evolution of 
oxygen by 
leaves be pro- 
ved by experi- 
ment ? 




872. The agency of the leaves of 
plants in absorbing and decomposing car- 
bonic acid, may be illustrated by the simple 
means represented in the figure. A glass 
funnel being filled with leaves and slightly 
carbonated water, is exposed to the sun. 
Oxygen gas is gradually evolved from 
the absorption and decomposition of the 
carbonic acid, and collects in the tube 
of the funnel. The oxygen may be 
tested by the usual means. The inversion of the fun- 
nel without loss of its contents, is easily effected, by 
covering it with a saucer and turning it in a pail of 
water. 

873. For certain transformations of ma- 
terial in plants, the evidence is entirely con- 
clusive. The sugar beet and turnip are 

sweetest in the earlier stages of their growth. Later 
in the year they become hard and fibrous. This change 
is undoubtedly owing to the conversion of the sugar 
contained in the sap into woody fibre. In the ripening 
of grain, the sweet and milky juice of the young plant 
is converted into starch. Both hay and grain which 
are harvested too late, are deteriorated by the conver- 
sion of a portion of their starch and sugar into wood. 
In the ripening of fruits a portion of their acid is con- 
verted into sugar, as is evident from their change of flavor. 

874. Office of the root. — The agency 
of the roots in supplying the plant with its 
mineral food, may be illustrated by the 
apparatus represented in the figure. In 



What traris- 
formations oc- 
cur in plants? 



How is the ac- 
tion of the 
roots illuS' 
trated by ex- 
periment $ 



preparation for the experiment, a glass fun- 




348 ORGANIC CHEMISTRY. 

nel is tightly covered with a piece of blad- 
der, and then filled with a solution of sugar 
or salt. A tube is then fitted, air tight, to 
its extremity. A glass vial, from which 
the bottom has been removed, may be sub- 
stituted for the funnel in this experiment. 
On placing the apparatus, thus arranged, in a 
vessel of water, the latter penetrates the ani- 
mal membrane, and adds itself to the con- 
tents of the funnel. The flow of the water 
is called endosmose, and is made apprecia- 
ble to the eye by the rise of liquid in the tube. An 
cxosmosc, or flow of a small portion of the contents of 
the funnel outward, takes place at the same time. 

875. The phenomenon exhibited in the 

Explain the . . 

phenomenon above experiment, is to be accounted for 
of endorse. by the difference of ca pillary attraction in 

,he bladder for the two liquids. The spongioles, with 
A'hich the extremities of the roots are provided, being 
filled with solutions of gum and. sugar, act similarly 
^pon the liquids of the soil. The endosmotic action, 
above described, is not confined to the roots of plants, 
but occurs in all their organs, through the walls of the 
minute cells of which they are composed. In connec- 
tion with the transpiration of water from the leaves, 
it is probably the principal cause of the circulation of 
the sap. The relation of the plant and soil is further 
considered in a subsequent chapter. 

876. Constituents of plants. — Among 

Mention some . i 

of the more the more important ot vegetable substances 
J3ES** are wood, starch, sugar and gluten. Woody 
stance*. fibre forms the mass of the plant ; starch 






wood. 349 

and gluten collect in the seed ; while sugar and gum 
exist principally in the sap and fruit, or exude from 
the bark. 



WOOD. 
Mention dif- 877 ' W °° DY FIBRE.— Woody fibre, of 

ferent forms which the fibrous threads of cotton or flax 

of woody fibre , , r 

—its com- ma Y serve as an example, is composed of 
position. carbon, hydrogen and oxygen. Its mole- 

cule contains twelve atoms of carbon, to ten of hydro- 
gen and ten of oxygen. It constitutes the solid mass 
of all vegetable organs, whether hard and firm, like 
the fibre of the oak ; soft, like the pulp of fruits ; or 
fibrous, like cotton and flax. In one or the other of 
its varieties it thus serves us for shelter, clothing and 
food. It forms in plants the cells in which the vege- 
table juices are contained, and the veins or pores 
through which they circulate : and has thence received 
its name of cellulose. In wood, these cells are often 
lined or filled with a substance of similar composition, 
to which the name of lignin has been given. 

878. Change by heat — gas, char- 

How is it 

changed by coal, etc. — Under the influence of 
a high temperature, without access 
of air, wood is converted into charcoal, water, 
gases, wood vinegar and tar. It is to be observed 
that this change is the simple result of a re-ar- 
rangement of the atoms of the wood itself, with- 
out the help of additional oxygen or other ele- 
ments. It is a most remarkable instance of va- 



350 ORGANIC CHEMISTRY. 

riety as produced by varied arrangement. The new 
substances are, as it were, different patterns woven 
from the same colored threads. The gases, of which 
carbonic acid, light and heavy carburetted hydrogen 
are the principal, have been already described. Wood 
vinegar and wood tar form the subjects of subsequent 
paragraphs. An excess of carbon remains behind as 
charcoal. The process is called dry distillation. The 
decomposition may be illustrated with saw-dust, in a 
test tube, as previously described. 

879. Similar change in nature — peat. 

Mention a si- . 

milar change Jreat is formed by the decay of vegeta- 
m nature. j^ e matter under water. The green slime 
which forms, in the summer, upon stagnant water is 
composed of minute plants. These die, each season, 
and sink to the bottom, until, in the course of years or 
ages, vast accumulations of vegetable matter are the 
result. By their partial decay or putrefaction under 
water, they are converted into peat. The process is 
analogous to that of dry distillation and the products 
similar. Carbonic acid and carburetted hydrogen gases 
are evolved, while a solid residue of peat remains be- 
hind. It may be regarded as a half-formed charcoal. 
Peat contains, in addition to its carbon, a little hydro- 
gen and a still smaller proportion of oxygen. The 
carbonic acid evolved in the above process often makes 
its way to the surface, at some neighboring locality, 
in the form of a mineral spring. 

880. Bituminous coal. — The formation 

Howisbitumi' „ _ . . , - - , . 

nous coal of bituminous and anthracite coal is a con- 

formed? sequence of a similar decay of vast accu- 






wood. 351 

muiations of vegetable matter which have been buried 
in the earth during previous ages of its existence. As 
a consequence of pressure, the material takes a different 
form from that already described, and is found, after 
ages have elapsed, as bituminous coal. 

Howisanthra- 881. ANTHRACITE COAL. Where bitll- 

cite formed? mous coal has been subjected to great heat, 
more carbon and hydrogen are expelled and anthracite 
coal remains. A similar change takes place where bi- 
tuminous coal is heated by artificial means. The coke 
which remains, is, like anthracite coal, nearly pure car- 
bon. 

882. Production of humus. — Humus 

What is hu- 
mus? How is or the vegetable mould of forests, is formed 

it pro uce . ky ^ decay of wood or vegetable matter 
in the air. Such decay is a species of slow combus- 
tion. The carbon is more slowiy consumed than the 
other constituents. The vegetable mould- or humus 
which remains after the partial decay, is, therefore, like 
peat, much richer in carbon than the material from 
which it was produced. It is variable in composition 
according to the progress of the decay. The access 
of oxygen from without being unlimited, it is found to 
remain in pqual atomic proportion with the hydrogen. 

What is the 883. WHITE ROTTEN WOOD. White 

composition of ro tt en wood, which forms in stumps and 

white rotten r 

wood? the interior of trees where there is abun- 

dant moisture and deficient access of air, has a different 
composition. The water present becomes chemically 
combined, and the product may be regarded as differ- 
ing from the former, somewhat as a hydrated oxide 
differs from the oxide itself. 



o52 ORGANIC CHEMISTRY. 

884. Preventives of decay. — The ten- 

How may the 

decay of wood dency of wood to decay is checked by 
eprevente . ac i(js, and also by certain salts. For 
this purpose, corrosive sublimate and chloride of 
zinc have been chiefly used. The process of impreg- 
nation with metallic salts is called kyanizing. 

885. Incombustible cloth. — Cotton 

How is cloth i * . • • 

rendered in- cloth immersed in a solution of phosphate 
combustible? Q f ma g nesia j s thereby rendered incombus- 
tible. Silicate of potassa is also used on wood for the 
same purpose. 

886. Effect of sulphuric acid on 

What is the . 

effect of sul- wood. — Sulphuric acid chars or blackens 
i J oodr Cid ° n wood b y abstracting a portion of the 
oxygen and hydrogen which it contains. 
The carbon is then left in excess, with its characteris- 
tic color. This action of sulphuric acid is a conse- 
quence of its strong affinity for water, the element? 
of which it appropriates from most organic substances 
Dilute sulphuric acid has another remarkable effect, t< 
be hereafter mentioned. 

887. Effect of nitric acid. — Nitric 

What is the ••,-,,, i t t 

effect of nitric ac id gradually consumes wood and othe? 
acid on wood? organic matt er, as effectually as if they 
were burned by fire. The final products of its action 
are also the same as those of ordinary combustion. 
This action is accompanied with the evolution of orange 
fumes, as when the same acid acts on metals. The 
first effect of nitric acid is to stain wood yellow ; for 
which purpose it is sometimes employed. Nitric acid 
may also be made to combine with woody fibre, form- 
ing gun cotton. 



wood. 353 

What is the 888. EFFECT OF MURIATIC ACID. This 

ShX acid add haS 110 Vei T Strikin S effeCt 011 W00d 

on wood? or other organic substances. But chlorine 

decomposes and destroys them ; principally, in conse- 
quence of its affinity for hydrogen, as before explained. 

What effect ^^' EFFECT 0F ALKALIES. Alkalies 

have alkalies have the effect of hastening the decompo- 

on wood and . . 

similar sub- sition of organic substances. This effect 
is, in part, due to the fact that they promote 
the absorption of oxygen from the air. Paper or cloth 
in contact with lime or potash, is found to lose its 
strength speedily, and finally to crumble away. The 
theory of this action has already been given in the 
paragraph on nitrate of lime. Where the atmosphere 
is excluded, it would seem, from certain experiments, 
that lime has an opposite effect, and rather retards than 
promotes the decomposition of organic matter. 
What differ- ^90. Wood vinegar. — The acid pro- 

en* substances duct, as obtained in the dry distillation 

are contained , . . , . . , , 

in wood vine- oi wood, contains, beside acetic acid and 
gar - water, a sort of alcohol, called wood- 

spirit, and an oily colorless fluid called kreosote. The 
latter has the odor of smoke, and has the same 
effect in preventing the putrefaction of animal sub- 
stances. This effect of smoke is owing, indeed, to the 
kreosote which it contains. A dilute solution of this 
oil in water is used in medicine and for curing meats. 
891. Wood tar. — Wood tar is a mix- 
\Mat9Hb*tan- t Q f var j cus \\ s and volatile crystalline 

v & are con 

tained inwood solids composed principally of carbon and 

hydrogen. Kreosote, which is also ob- 



354 



ORGANIC CHEMISTRY. 



tained from wood vinegar, is one of the oils. Another 
of them, called enpion, has a pleasant odor somewhat 
similar to that of the flower called narcissus, Pittacal, 
a beautiful blue coloring matter, resembling indigo, and 
paraffine resembling spermacetti, are also obtained from 
tar. 

892. Coal tar. — Coal tar 
JatlZre is produced from bituminous 

contained in coa ] [ n th e process of mak- 

coal tar ? 

ing illuminating gas. It con- 
sists of numerous liquid and solid hydro- 
carbons produced by the decomposition 
of the coal from which it was formed. 
Among them is napthaline, like camphor 
in appearance, and dissipated, like this sub- 
stance, by exposure to the air. Others are 
mentioned in the next paragraph. Coal tar, mixed 
with chalk or other material, is used as a cement, and 
also as a material for covering roofs. 

893. Useful, products from coal 
2$d2rT" tar.— The first product of its distillation 
ducts of coal i s a light oil commonly known as benzole. 

This may be substituted for spirits of tur- 
pentine for a great variety of uses. Another heavier 
oil which is obtained from it, is used as a solvent of 
india-rubber, and also for lubrication and illumination. 
In Europe, the pitchy mass, which remains on dis- 
tillation, is employed in moulding refuse coal dust 
into cakes to be used as fuel. The light oil is also con- 
verted by the action of nitric acid into an artificial es- 
sence, similar to that of bitter almonds, used exten- 




wood. 355 

sively for scenting soap. Its vapor, mixed with air, is 
also burned as gas. The heavy oil may be converted 
by a different action of the same acid, into beautiful 
lemon-colored crystals of carbazotic acid, a substance 
now used in France as a yellow dye for silks and wool. 

894. Oils from coal. — The oils may 

How arc oils 

produced from be directly produced from bituminous coal 
itself, and in much larger quantities than 
from tar, by avoiding the high temperature to which 
coal is subjected in the production of tar and gas. 
The production of oils by this means promises to 
be a very important branch of industry. 

895. Gun-cotton. — This material, so 

How is gun- , 

cotton pre- entirely harmless in appearance, has an 
pared? explosive energy superior to that of gun- 

powder. It may be prepared by immersing ordinary 
cotton, for the space of five minutes, in the strongest 
nitric acid. It is then to be washed thoroughly, and 
dried at a moderate heat, for fear of explosion. The 
material is found to have lost a certain portion of its 
oxygen and hydrogen, in the form of water, and to 
have assumed nitric acid in its place. It is not how- 
ever changed in its appearance. A mixture of nitric 
acid with two-thirds of its volume of oil of vitriol is 
found to be preferable to pure nitric acid in the above 
experiment. The oil of vitriol assists in abstracting 
from the cotton the water which it is desired to replace 
by nitric acid. Gun-gotton is also called pyroxyline. 
Similar compounds, which are less explosive, may be 
prepared from sugar and starch. 



356 ORGANIC CHEMISTRY. 

un . . , 896. Use of gun-cotton. — Gun-cotton 

What is said . . •*-***■ 

of its proper- is not likely, for several reasons, to super- 
cede gun-powder for use in fire-arms. It 
is much more expensive, and so suddenly explosive as 
often to burst the barrels in which it is fired. Its ex- 
plosive force depends, like that of gun-powder, on a 
sudden combustion throughout its whole substance, 
and consequent evolution of a large volume of mixed 
gases and vapor. Of these, carbonic acid, nitrogen and 
aqueous vapor are the principal. 

897. Gun-cotton solution — collodi- 

W hat is collo- 
dion? How is on. — Gun-cotton dissolves in ether, form- 
ing a syrupy liquid which on evapora- 
tion leaves behind a transparent, tenacious film. It is 
used, to some extent, in place of ordinary court-plaster, 
for covering wounds and protecting them from the air. 
tj , 898. Wood converted into sugar. — 

How may wood 

be converted Wood may be converted into sugar, by caus- 
ing it to combine, chemically, with four ad- 
ditional molecules of water. This addition gives it the 
precise composition and properties of grape sugar, and, 
in fact, converts it into that substance. Poplar wood is 
found best suited for the purpose, and can be made to 
yield four-fifths its weight. To effect the conversion, 
the wood is first reduced to saw-dust, then moistened 
with somewhat more than its own weight of oil of vit- 
riol, and left to stand for twelve hours. Being subse- 
quently pounded in a mortar, the nearly dry materia! 
becomes liquid. It is then boiled with addition of 
water, and the transformation is completed. It only 
remains to remove the sulphuric acid, and evaporate 



STARCH. 357 

the syrup. The former object is effected by the addi- 
tion of chalk and subsequent filtration, and the latter, 
as usual, by boiling 
it • j 899. Wood converted into gum. — 

rLow is wood 

converted into If the boiling be omitted in the above pro- 
cess, the woody film takes the form of a 
gum, called dextrine, of the same composition as the 
wood itself, but soluble in water. Linen or cotton 
rags, or paper, may be converted into sugar or gum 
by the same process. The sugar obtained is the same 
as that contained in grapes, and is therefore called 
grape sugar, and also glucose. It differs, somewhat, 
from ordinary cane sugar, as will be hereafter explained. 

STARCH. 

What is said 000. Description. — Starch is identical 

of the compo- [ n composition with wood and gum. It 

sitwn and ' . 

structure of consists of minute enveloped grains, which 
burst and discharge their contents when 
swollen by warm water. 

Where is 901. — Occurrence. — Starch is found 

starch foundi [ n abundance in most grains and other 
seeds ; in the tubers of the potatoe plant ; in many 
fruits, and in the pith of certain trees. In greater or 
less quantity, it is contained in all substances of vege- 
table origin which are used as food. Horse chestnuts 
contain 12 per cent, of starch, and have been used in 
Europe for the production of flour. 

902. Starch from potatoes. — Starch 

How is starch 

prepared from is prepared from rasped potatoes by wash- 
potatoes? j n g t j iem on a se i V e. The water becomes 







358 ORGANIC CHEMISTRY. 

milky, as it passes through, from the fine starch grains 
which it carries with it. These are allowed to settle, 
and being collected and dried, are brought into com- 
merce as potatoe starch. A cotton-cloth may be sub- 
stituted for the seive in this experiment. 
rr . , 903. Starch from wheat. — If wheat 

How is starch 

made from flour is moistened with water and exposed 
to the air, it enters into" a putrefaction which 
destroys, in the course of a few days, the 
other constituents and leaves the starch un- 
affected. The residue being then washed 
and dried, the manufacture is completed. Io- 
dine may be used as a test for starch, as described under 
the head of iodides. Gums and woody fibre, although 
:>f the same composition, are not similarly affected. 

904. Conversion of starch into 
converted into sugar. — Starch, like woody fibre, may be 
sugar. converted into sugar through the agency 

of sulphuric acid. A dilute acid containing only j\ of 
its volume of oil of vitriol, is brought to the boiling 
point, and the starch then added by degrees while the 
boiling continues. Long boiling is required to effect a 
complete conversion. An infusion of brewer's malt has 
the same effect as the dilute acid. The sulphuric acid 
is then to be removed, and the syrup concentrated as 
before described. The sugar in this case also is grape, 
and not cane sugar. Such sugar is manufactured largely 
in Europe for adulterating cane sugar. In England 
its manufacture is prohibited by law. 

905. Conversion of starch into gum. 
transformed By keeping the liquid near to the boiling 
into gum? point> without actual boiling, the gum 



SL'GAR. 359 

called dextrine, is obtained in the above process, instead 
of sugar. It may also be prepared by roasting starch, 
carefully, with constant stirring, until it acquires a 
brownish yellow color. This gum is used largely in 
calico printing, for thickening colors. It is also used in 
making the so-called " fig-paste " and certain other 
kinds of confectionery. The composition of starch 
and gum is precisely the same. 
TT ^ 7 . . , 906. Gum. — Gum arabic and the gum 

what is said . ° 

of natural of fruit trees generally, is identical in com- 
gums. position with woody fibre and starch. 

They are either soluble, like gum arable, in water, or 
swell up with it to form a thick paste, like gum traga- 
canth. The substance called pectine, which causes 
the juice of currants and other fruits to stiffen with 
sugar into a jelly, is also similar to the above sub- 
stances in composition. All of these bodies, like wood 
and starch, are convertible into sugar by the action of 
sulphuric acid. 



SUGAR. 

Where does 90r - Grape sugar.— The production 

grape sugar of this substance from wood and starch has 

occur * 

already been described. It does not exist 
in the juice of grapes, as its name would imply. The 
sugar of the grape and other acid fruits contains two 

molecules less of water. This is spontaneously convert- 
ed into true grape sugar or glucose, and found in in- 
crustations upon the surface of the dried fruit. Those 
fruits and trees which have but little acid in their 

1G 



360 ORGANIC CHEMISTRY. 

juice or sap commonly contain cane sugar. The 
sweetness of honey is due to grape sugar. This va- 
riety is much less valuable than that of the cane, from 
the fact that it has but little more than one-third of its 
sweetening effect. 
„„ . . , 908. Cane sugar. — The sugar in corn- 

What 9 s ^aid 

ofthecompo- mon use is principally derived from the 

S«r °fnd a us su S ar cane > and thence receives its distinc- 
ar'ificiai pro- tive name. It differs in its composition 
from starch, wood and gum, in containing 
a single additional molecule of water ; while grape sugar 
contains four. It would seem from this com- 
position, that it would be more easily produced ((^ 
by artificial means from starch and similar 
substances. But this is not the fact. No 
modification of the process above described, 
has as yet been devised by which starch and wood can 
be induced to take one additional atom of water, in- 
stead of four. Such a process would be a discovery 
of the greatest importance, as it would enable us to con- 
vert our potatoe and grain fields at will into sugar 
plantations, and make us independent of foreign sup- 
plies. The figure represents a crystal of cane sugar 
The form belongs to the fourth system. 

909. Occurrence. — Cane sugar is 

WJiat are the . . __ _ _ 

principal principally produced from the sugar cane, 

sources of cane from beet and the American maple. But 

sugar ? r 

it is contained in smaller quantity in the 
sap of most plants, and in all fruits and vegetables 
which are not acid to the taste. The production of 
beet sugar in Europe, in 1850, was estimated at 190,000 



SUGAR. 36] 

tons. That of cane sugar in cane growing countries 
;s incomparably greater. 

910. Production. — In manufacturing 

How is cane . . . 

sugar pro- sugar from the cane, the juice is first pressed 
duced - out between heavy iron rollers, then clar- 

ified, and finally boiled down until it will crystalize on 
cooling. The granular crystals form the raw sugar ; 
>he drainings. molasses. Lime is the principal agent in 
clarification. Its first effect is to neutralize the acid of 
the juice, which, as before seen, would gradually con- 
cert the cane sugar into grape sugar, and thus injure 
Is quality. It also precipitates, with other impurities, 
(he gluten, which, as will be hereafter seen, tends to 
produce more acid. The methods of producing sugar 
from the beet and maple are essentially the same. The 
final purification of sugar by bone black has already 
been described. 

911. Molasses. — A large portion of 

Row may mo- . 

lasses be c<m- sugar is ordinarily lost in the form of mo- 
vertedinto i asses , from which it cannot be made to 

sugar f 7 

separate by crystallization. This is owing 
to the presence of impurities not separated by clarifica- 
tion which interfere with the process in a way not per- 
fectly understood. A method has recently been con- 
trived of avoiding the loss, and thus largely increasing 
the product of the beet and cane. Baryta added to the 
syrup combines with the sugar, and takes it to the 
bottom of the vessel as a solid compound of sugar and 
baryta, while the impurities remain behind. This pre- 
cipitate is then removed and diffused in water. Car- 
bonic acid being added, combines with the baryta, and 

16 



S62 ORGANIC CHEMISTRY. 

leaves the sugar to form a pure and crystallizable syrup. 
Another method of increasing the product of sugar has 
been described in the section on sulphurous acid. 

ALCOHOL. 
rr . . . _ 912. Production from sugar. — By 

How is alcohol j . . - ; J 

produced from the addition of brewers' yeast or some si- 
sugar? milar ferment to sugar, it is gradually con- 

verted into alcohol. Two molecules of water are sepa- 
rated in the process. One-third of the carbon and two- 
thirds of the oxygen which remain, pass off as carbonic 
acid gas, while alcohol is left. The yeast enters into 
no combination, and furnishes no material in the pro- 
cess. It acts merely by its presence to effect the de- 
composition, as will be hereafter explained. 
Explain the 913. In this process of conversion 3 each 

diagram. molecule of sugar makes two of alcohol and 

four of the acid. The figure repre- 
sents a molecule of grape sugar after 
the removal of two molecules of 
water. An arbitrary arrangement is 
given to the atoms for convenience 
of illustration. On striking off 
enough carbon and oxygen from the 
corners to make the required amount 
of carbonic acid, the residue may be supposed to fall 
apart into two molecules of alcohol. Alcohol is also 
produced from cane sugar by fermentation. The first 
stage in the process is its conversion, by yeast, into 





ALCOHOL. 363 

grape sugar. The latter is then changed into alcohol 
and carbonic acid, as above described. 

914. Composition. — The composition 

What is the . 

composition of of alcohol appears sufficiently from the mid- 
dle groups of the preceding figure. Accord- 
ing to the theory of compound radicals 
it is a hydrated oxide of ethyle. The 
principal group of the annexed cut, 
represents a molecule of the radical ; wlPPww vJ 
the remaining circles stand for the oxygen and water 
with which it is combined in alcohol. 
tt ■ i -l i 915. Production from potatoes and 

Mow is alcohol 

made from po- grain. — Where molasses or solution of 
sugar is the material used, alcohol is pro- 
duced as already shown. But when potatoes and grain 
are employed as the material, a previous process is 
necessary by which the starch is converted into sugar. 
This consists in the addition of bruised malt to the 
mashed potatoes or grain. The diastase of the malt 
has the effect of gradually transforming starch into 
sugar by its presence, as yeast converts sugar into 
alcohol. The mixture being kept at a temperature 
of about 140°, in a few hours the transformation is 
complete. The starchy mixture has become sweet, 
and receives the name of wort. Brewers' yeast and 
water being then added to the wort, the conversion into 
alcohol commences. This is afterward separated from 
the water and refuse fibre of the potatoe or grain by 
the process of distil .ation. described in a subsequent 
paragraph. 



S64 ORGANIG CHEMISTRY. 

What is said ^16. Production from illuminating 

of the prodnc- GAS# — Alcohol may also be produced from 

Hon of alcohol r 

fromolefiant heavy carburetted hydrogen, one of the con- 
gas ' stituents of ordinary illuminating gas. This 

is one of the most remarkable results of modern science. 
Most of the processes of organic chemistry consist in 
taking apart the complex molecules of organic matter and 
reducing them to a simpler form, as was illustrated in the 
production of alcohol and carbonic acid from sugar. Na- 
ture, for the most part, jealously withholds from man 
the power so to direct her forces as to build up and 
produce more complex organic substances by the com- 
bination of those of simpler nature. This takes place 
as a general rule only under the influence of the vital 
forces of vegetable and animal existence, as when the 
plant produces sugar from the elements of the atmos- 
phere. 

Explain Us 917. By reference to the central group 

production. f t ; ie figure, which represents a molecule 
of heavy carburetted hydrogen, it will be seen that all 
that is necessary to effect its conver- 
sion into alcohol, is the addition of 
two molecules of water. By long 
agitation of the gas with strong sul- 
phuric acid, the transference of part of the water which 
it holds combined is effected. On subsequent dilution 
and distillation, alcohol is obtained from the mixture. 
Carbonate of potassa is added in the process of distil- 
lation, to diminish the proportion of Avater which would 
otherwise pass off with the alcohol. After repeated dis- 
tillation strong alcohol is thus obtained. 





ALCOHOL. 365 

_ . ._ 918. Distillation of alcohol. — The 

W hat is said 

of the process process of distillation may be illustrated 
of distillation? wkh the gimple apparatus rep resented in 

the figure. On heating wine, cider or beer in the test- 
tube, its alcohol will be ex- 
pelled as vapor and re-con- 
densed as a colorless liquid. 
The cooler the vial is kept 
the more perfect is the condensation. The apparatus 
commonly employed in the distillation of alcohol, con- 
sists of a large copper vessel in which the fermented 
wort is heated, and a long tube called the worm, in 
which the vapors are condensed. The worm is made 
to wind in a spiral, through a tub of cold water, that 
the condensation may be more completely effected. 
The spirit pours out at the lower end of the worm, 
where it emerges from the tub. It may be strength- 
ened by repeated distillation. In order to obtain it 
entirely free from water, a highly rectified spirit is 
mixed with lime, or chloride of calcium, and re-dis- 
tilled. These substances have such affinity for water, 
that they prevent its escape as vapor, while they in 
no wise effect the distillation of the alcohol. By 
this means pure alcohol, or absolute alcohol, is ob- 
tained. 

What U spiv 919 - UsES 0F alcohol— Ordinary 

its of wine? spirits of wine is a dilute alcohol contain- 

Mcntion some - 

ris?s of aico- ing but about seventy per cent, of absolute 
ha - alcohol. The taste and odor of alcohol, 

its combustible character, and action as a stimulus, are 
too familiar to need further mention. Its density and 



366 ORGANIC CHEMISTRY. 

boiling point are given in the Appendix. It is largely 
used in medicine, and as a solvent of oils and resins 
and many other substances which water does not dis- 
solve. Medicinal extracts of many roots and herbs, 
" cologne," and other perfumed liquids are thus pro- 
duced. 

What is the ^20. SPIRITUOUS LIQUORS. SpiritUOUS 

source of the liquors contain alcohol in large but varying 

different spir- . . . ° 

ituousli- proportion. They diner m their flavor 

9nors ' according to the material from which they 

are produced. Brandy is distilled from wine, rum 
from molasses, and whiskey from malt liquors. The 
latter name is also given, in this country, to the liquor 
made from potatoes, corn, and rye. In Europe, the 
latter are more commonly called brandies. 
How are wines 921. Wines. — Wines are produced by 

produced ? ^ ie fermentation of the juice of the grape. 
On exposure to the air, the gluten of the juice becomes a 
ferment, and causes the conversion of the sugar into 
alcohol. The addition of yeast is therefore unneces- 
sary. This is also true of the juice of the apple, pear, 
and other fruits from which fermented liquors are sim- 
ilarly produced. 

How is cham- 922. Ohampagne.— Champagne and 

pagnemade? other sparkling wines owe their peculiar- 
ity to the presence of carbonic acid in large propor- 
tion. This is secured by allowing the last stages of 
fermentation to proceed in firmly corked bottles, so 
that all the gas which is evolved is retained. Or an or- 
nary wine is first produced by the usual process, and 
sugar and yeast are then added, to excite a new fer- 
mentation in the bottled liquid. 



MALT LIQUORS. 367 

What is said ^23. "Alcohol in wines. — Wines differ 

of the pro- i n the amount of alcohol which they con- 

portion of al- J 

coholin tain; from five per cent., in the weakest 

champagne, to twenty-five, in the strongest 
sherry. Those of southern climates are strongest, be- 
cause the grapes of those regions contain more sugai 
to undergo conversion into alcohol. Most wines also 
contain more or less acid and unfermented sugar. 
What is said 924. Tartar. — The acid of wine is 

of acid in . , - . , . 

wines? tartaric acta, which exists in combina- 

tion with potash in the juice of the grape. It grad- 
ually deposits in wine casks in the form of acid tar- 
trate of potash or cream of tartar. This separaton 
of tartar is one source of the improvement of wines, 
and more particularly of the rhenish wines, by age. 

925. Flavor of wines. — The wine 

What is said . ♦ 

of the flavors flavor which belongs to all wines, is 
of wmes? owing to the presence, in extremely small 
portion, of an etherial liquid called aenanthic ether. 
This substance does not exist ready formed in the 
grape, but is produced in the re-arrangement of atoms 
which takes place in fermentation. Its vinous odor, 
when separated from the wine, is most intense. It is 
prepared in Europe from grain spirit or cheap wines, 
and is used in this and other countries for producing imi- 
tations of wines of higher price. Potatoe whiskey is 
commonly the basis of these manufactured wines. 
Beside the general vinous flavor, different wines, like 
flowers, have an aroma or bouquet peculiar to them- 
selves. These are owing to other and different flavor- 
ing substances, present in still smaller proportion than 
the aenanthic ether. 



368 ORGANIC CHEMISTRY. 

926. Beer and ale. — Beer is the fer- 

How arc malt 

liquors pre- merited extract of malted grain. The malt 
pare is prepared by softening barley in water, 

and then allowing it to sprout or germinate. Diastase, 
which is formed in the process of germination, con- 
verts the starch of the grain into sugar, and thus pre- 
pares it for the subsequent process of fermentation. 
Yeast and hops are added to the extract of malt, which 
is called the wort, to bring about fermentation and 
help to give the product flavor. Ale is a similar malt 
liquor of different color. Porter is a darker variety of 
beer, made from malt which has been browned by 
roasting. 

927. Conversion of alcohol into 

How is alcohol k , . . . , , . t . 

converted into ether. — Alcohol is converted into ether 
ether I ^y heating with oil of vitriol. To illus- 

trate its preparation, equal 
volumes of strong alcohol 
and oil of vitriol may be 
thoroughly mixed in a test- 
tube, and the vapors con- 
densed in a cool vial, as J 
represented in the figure. 
A little sand may be added to the mixture with advant- 
age. The vial should be kept cool by means of paper 
repeatedly moistened during the process. The space 
between the tube and the neck of the vial should also 
be loosely closed with wet paper. 

928. Explanation. — Alcohol is, as 
above re-ac- above stated, the hydrate of the oxide of 
iion ' ethyl. Sulphuric acid combines with the 





ETHYL. 369 

oxide itself, on heating, forming a bi- 
sulphate, and at a little higher tem- 
perature, yields it up again, as gaseous 
ether or oxide of ethyl. The change 
in the alcohol consists, simply, in the loss of an atom 
of water. The whole figure represents a molecule of 
alcohol ; the lower portion one of ether. 

929. Production of ethyl. — The 

How is the 

radical ethyl radical ethyl cannot, J ike many metals, be 
procured? directly produced from its oxide, Heat, 
or other means, applied to accomplish this object, 
destroys the radical itself. But the end may be 
reached by a circuitous process. This consists in first 
producing from the oxide, an iodide 
of ethyl, and then removing the iodine 
by a metal. A colorless gas, of the 
composition indicated by the hydrogen and carbon at- 
oms of the figure, is thus evolved. 

930. Conversion of alcohol into 

How is alcohol 

converted into OLEFIANT GAS. The production of alcO- 

olefiantgas? ho j frQm olefiant gag has beeR described 

in the section on hydrogen. The subject is again in- 
troduced for the purpose of illustrating the change, by 
reference to the atomic composition of the two sub- 
stances. Representing the atom of 
alcohol as before, it is converted by 
the removal of two atoms of oxy- 
gen, and two of hydrogen, into olefi- 
ant gas. The composition of this gas is indicated by 
the central group of the annexed figure. The ab- 
straction of oxygen and hydrogen is effected through 
16* 





370 ORGANIC CHEMISTRY. 

the agency of the sulphuric acid used in the process. 
It will be observed that the radical ethyl, which has re- 
mained permanent in the changes before described, is 
here destroyed by the abstraction of a part of its hy- 
drogen. 

Wliatis aide- 931. CONVERSION OF ALCOHOL INTO ALDE- 

hyde? hyde. — Aldehyde is a clear colorless liquid 

of a peculiar ethereal odor, produced by the action of 
the air or oxygen on alcohol. It is the product of a 
partial, slow combustion, or ererne- 
causis of the alcohol, and forms the 
middle point in the conversion of 
alcohol into vinegar. It is for this 
reason that it is here introduced. 

932. The two atoms of hydrogen 

How is alcohol «, . , ■* j A . ,,, 

converted into which are burned out m the process, are 
aldehyde f indicated in the figure by smaller inscribed 
letters. By the removal, the radical ethyl is converted 
into the radical acetyl. Aldehyde is therefore a hy- 
drated oxide of acetyl. The characteristic odor of the 
substance is often perceived in the process for making 
vinegar. It may also be produced by depressing a wire 
gauze upon an alcohol flame, and thereby making the 
combustion incomplete. 

933. Conversion of alcohol into vin- 
Hxplainthe EGAR — If dilule a i co h i j s exposed to the 

conversion oj L 

alcohol into a i r? it is converted, by oxidation, into ace- 
vmegar ^ ac ^j p art £ j ts hydrogen having been 

burned out to form aldehyde, the oxy- 
gen acts further to oxidize the alde- 
hyde which has been produced. The 
composition of each molecule is such 




VINEGAR. 371 

as is represented in the preceding figure. It will be ob- 
served that the oxygen added is just sufficient to sup- 
ply the place of the hydrogen removed in the formation 
of aldehyde. The latter substance being a hydrate of 
the protoxide of acetyl, acetic acid is a hydrated terox- 
ide of the same radical. The presence of yeast or 
some other similar ferment, is essential in the produc- 
tion of vinegar as well as in that of alcohol. 

Describe the 934. PROCESS OF MANUFACTURE. A. 

process. f ew y ears since, vinegar was exclusively 

produced by the souring of wine or cider. At pres- 
ent, large quantities are made from alcohol, by diluting 
it with water, adding a little yeast, and then exposing 
it to the action of the air. This is best accomplished 
by allowing the diluted alcohol to trickle through shav- 
ings packed in well ventilated casks. A few passages 
through the cask suffices to convert the liquid into 
vinegar. The addition of yeast is unnecessary in pro- 
ducing vinegar from cider or wine, as these liquids con- 
tain a substance which acts as a ferment. The vapor 
of alcohol may be readily converted into acetic acid 
by contact with platinum black. The property of pla- 
tinum to produce oxidation in similar cases has been 
already explained. 

935. Chloroform. — Chloroform is best 

How is chloro- ,-.--,, ,. .,,. 1 , 1 . , 

formprepar- obtained by distilling pure alcohol with 
ed? Mention and bleaching p0 wder. Its mole- 

its properties. ° r 

cule consists of two atoms of carbon, and 
one of hydrogen, combined with three of chlorine. The 
carbon and hydrogen atoms are regarded as more inti- 
mately combined to form the radical formyl. Chloro- 



372 ORGANIC CHEMISTRY. 

form is therefore a terchloride of this radical. It is 
a colorless and volatile liquid, of a peculiar, sweetish 
smell. The inhalation of its vapor produces insensi- 
bility to pain, and is much employed in surgical ope- 
rations for this purpose. Ether has the same effect 
in a less degree. A mixture of the two is more com- 
monly employed in this country. 
T , , 936. Fusel oil. — Fusel oil is a peculiar 

WJlf.lt IS fllSel 

oil? Mention kind of alcohol, of extremely nauseous 
its properties. Q ^ QY an( j p i sonous properties, which ac- 
companies ordinary alcohol in its production from 
potatoes and grain. It may be separated by filtration 
through charcoal. But this process of purification is 
often neglected, and the fusel oil left to add its poison 
to the deleterious effects of the alcohol itself. It is 
this doubly poisonous alcohol which forms the basis 
of numerous manufactured liquors, wines and cordials. 
Fusel oil is the hydrated oxide of amyl. This radical 
contains ten atoms of carbon to eleven of hydrogen. 
It belongs to the series of alcohols mentioned in the 
first chapter of organic chemistry. 

ORGANIC ACIDS. 

mat is said 937 - Acetic acid.— Ordinary vinegar 

of theproduc- i s a dilute acetic acid. It cannot be con- 
tort and prop" 
ertie* of acetic centrated by evaporation, as the acid is 

volatile as well as the water which dilutes 

it. To obtain the strong acid, recourse is had to the 

sails of acetic acid, from which it is prepared by the 

method used for nitric and muriatic acids. The pure 



TANNIC ACID. 373 

acid is a solid. It mixes with water at low tempera- 
ture, in all proportions, and is commonly seen in its dis- 
solved state. Its compounds with metallic oxides are 
called acetates. The sugar of lead, so called, is an 
acetate, formed by dissolving litharge in acetic acid. 

938. Tannic acid. — Tannin, or tannic 
Mention the acid exists in nut-sails and in the bark 

source ana ' o 

properties of and leaves of many trees. It is the prin- 

tannic acid. . . . . . . . . 

ciple which imparts to them their astrin- 
gent taste, and gives to the tan liquor the property of 
converting hides into leather. When separated from 
the other substances with which it is combined in 
nature, it is a yellowish, gummy mass. It is soluble in 
water, and possesses the property of precipitating glue 
or gelatin, and many other metallic oxides. 

939. Writing ink. — Common writing 

What is the . 

coloring mat- mk is prepared from nut-galls and proto- 
f ik °{ writin9 sulphate of iron. When first made, it is 
principally a tannate of the protoxide of 
iron, and forms a very pale solution. Before 
it is fit for use, it must be exposed for a time 
to the air, and thereby converted, partially, into 
tannate of the peroxide. This is a bluish black 
precipitate, and imparts to it the requisite color. 
It is essential to the permanence of ink, that 
the change should take place, in part, in the fibre of 
the paper itself. Too long exposure should, therefore, 
be avoided in the manufacture. The pale ink thus 
produced, which blackens further in using, is much more 
permanent than a thicker, darker ink, produced when 
this caution is not observed. 







374 



ORGANIC CHEMISTRY. 



_ 940. Six parts of nut-galls to four of 

G"tVC the X)YO~ 

cess of its copperas, are found to be the best propor- 
preparation. tiong f()r producing a permanent ink. The 

galls are to be boiled with water, the decoction strained, 
and mixed with copperas solution. Gum and cloves 
are added, the former to keep the coloring matter of the 
ink from settling, and the latter to prevent its moulding. 
After a ripening of a month or more the liquid is 
strained. The coloring matter of ink is immediately 
produced in a solution of copperas, as a bulky precipi- 
tate, by the addition of tincture of galls and a little 
nitric acid. 



Mention the 
composition 



HYDROCYANIC ACID. 

941. Cyanogen. — Before proceeding 
with the description of hydrocyanic, or 
lf%7no e get. S P russic acid > the production of cyanogen, 

which enters into its 
composition, will be briefly consid- 
ered. Cyanogen is a colorless gas, 
with a peculiar odor resembling 
that of peach pits. It is nearly twice 
as heavy as atmospheric air. It 
burns with a beautiful purple flame. 
Cyanogen is a compound radical, 
possessed of important analogies to 
chlorine and the other electro-neg- 
ative elements. Its molecule contains one atom of ni- 
trogen and two of carbon. 

How is cyano- 942. Production. — Cyanogen may be 
gen prepared? expelled from the cyanide of mercury by 




CYANIDES. 375 

the agency of heat. This metal retains cyanogen as 
it does oxygen, but feebly. A method more commonly 
employed is to produce and decompose the cyanide of 
mercury at the same moment. This is effected by 
mixing chloride of mercury, to furnish the metal, with 
the double cyanide of iron and potassium, which fur- 
nishes the cyanogen. The other elements unite to 
form chlorides of iron and potassium, while the cyanide 
of mercury is decomposed as fast as it is formed. The 
double cyanide of iron and potassium, above referred to, 
is the commercial yellow pmssiate of potash. Two parts 
of this salt are to be heated with one of bi-chloride of 
mercury, in the above process. The prussiate cannot 
be used alone for the production of cyanogen, on ac- 
count of the firm retention of this radical by the 
highly electro-positive metals which enter into the com- 
position of the salt. 
tt • 943. Cyanide of potassium. — Cyanide 

How is cya- J 

nide ofpotas- of potassium is a white substance, resem- 

sium prepar- _ , . , . . , 

ed? Mention bling porcelain in appearance, and quite 
it* uses. soluble in water and alcohol. It is largely 

employed in preparing solutions of the precious metals, 
for galvanic gilding and silvering. It is produced on a 
large scale, by fusing together carbonate of potash and 
refuse animal matter. The latter furnishes the carbon 
and nitrogen required for the production of cyangen, 
while the carbonic acid and oxygen of the salt, are 
principally evolved as oxide of carbon. The cyanide 
of potassium is best extracted from this residue by alco- 
hol, which leaves the other material undissolved. 



376 ORGANIC CHEMISTRY. 

How is yellow 944 P^SSTATE OF POTASH.— Cyanide 

prussiate of of iron is always incidentally formed from 

potash pre- . . 

pam*; i/e;i- the iron 01 the vessel in the above process. 

Hon its uses. j f water i§ adde( j to the fuged mass? both 

cyanides dissolve ; although the latter, when alone, is 
entirely insoluble. From the solution, the double cy- 
anide of potassium and iron, mentioned in a preceding 
paragraph, is obtained, by evaporation, in splendid yel- 
low crystals. It is known in commerce as yellow 
prussiate of potash, and is largely used in the arts for 
the production of prussian blue and cyanide of potas- 
sium. Prussian blue is obtained by adding its solution 
to a salt of the peroxide of iron. As any solution of 
iron is readily peroxydized by the addition of a little 
nitric acid, the yellow prussiate may be employed as a 
test for this metal. 
„ rT . . _ 945. Perrocyanides. — The yellow 

M hat is said 

of ferrocyano- prussiate of potash, produced as above de- 
gen scribed, is not properly a double cyanide 

of iron and potassium. There is reason to believe 
that the cyanogen is more intimately combined with 
the iron than such a name would imply. It seems to 
have lost its ordinary properties in the compound. 
Neither the alkalies or sulphide of ammonium, which 
usually precipitate iron from its solutions, have any 
power to precipitate it from this salt. The three mole- 
cules of cyanogen, which enter into its composition, 
seem to have hidden and absorbed it. They have 
formed with it, indeed, a new compound radical, called 
ferrocyanogen. The double salt above mentioned is 
therefore more properly a ferrocyanide of potassium. 



PRUSSIC ACID. 377 

Ferrocyanogen, like all other compound radicals, con- 
ducts itself, under ordinary circumstances, as an ele- 
mentary substance. 

Wltatisferri- 946. On the removal of one atom of 
cyanogen? potassium from two molecules of this salt, 
a coalescence of the ferrocyanogen of the two mole- 
cules seems to be the result, and a new compound radi- 
cal is formed. This radical is called ferricyanogen. 
It combines with the three remaining atoms of potas- 
sium, to form ferricyanide of potassium. 
Givetheprop- 947 ' Pmssic acid.— Hydrocyanic acid 
ertlefi of pms- j s made from cyanide of potassium, by the 

sic acid and • . 

it* mod* of same method employed for producing hy- 
preparation. drochloric ac j<i f rom common salt. The 

ferrocyanide of potassium is more commonly employed 
in the process. Prussic acid is intensely poisonous. A 
drop or two of the concentrated liquid, placed upon the 
tongue of a dog, produces immediate death. On ac- 
count of its extremely dangerous properties, the prepa- 
ration cf the acid should never be attempted except 
by a professional chemist. The odor of the acid is 
somewhat similar to that of cyanogen, and may be fre- 
quently detected in the vicinity of establishments where 
galvanic gilding is conducted. Ferrocyanogen and fer- 
ricyanogen, like simple cyanogen, have their hydrogen 
acids and series of salts. The acid of the former is 
bibasic, and that cf the latter tribasic, as already shown 
by the composition cf their potassium compounds. 
Whatissad ^48. Other organic acids. — Tartaric 

itrie, ma- acid, before mentioned, is found in the 

lactic, ox- 

alicy and for- grape. The acid tartrate of potassa or 
cream of tartar, which deposits in wine 



378 ORGANIC CHEMISTRY. 

casks, is one of its most important salts. Another has 
been mentioned under the head of antimony. Oxalic 
acid is found in wood sorrel and in certain lichens. It 
is also prepared by the action of nitric acid on wood, 
sugar and starch. When these substances are burned 
in the air, their carbon is converted into carbonic acid. 
Oxalic acid contains half the proportional quantity of 
oxygen, and may be regarded as the product of a less 
perfect combustion by the oxygen of nitric acid. It is 
a white crystalline solid and a most dangerous poison. 
The effect of heat on oxalic acid, with its precise com- 
position, is given in the section on Carbonic Oxide. 
Citric acid is the acid of lemons, malic acid, that of 
the apple, and formic acid that of the red ant. The 
latter may also be formed from wood spirit, by oxida- 
tion, through the agency of platinum black, as acetic 
acid is formed from ordinary spirit or alcohol. Lactic 
acid will be again mentioned under the head of animal 
chemistry. 

949. Their composition. — All of these 

IV^hctt zs tli6 

composition of acids differ in taste and in various chem- 

f atid*? V6 * ca * P ro P ert i es > as d° those of inorganic 

chemistry. Yet all of them contain the 
same three elements which are also contained in wood, 
gum and starch. They contain these elements in 
various proportion, but their peculiarities are not to be 
ascribed to this cause alone. They may be regarded 
as in part, at least, the consequence of a difference of 
arrangement of the atoms, as has already been ex- 
plained 



What i 



ESSENTIAL OILS. 379 

ESSENTIAL OILS. 

^ 950. Volatile, or essential oils.— 

of the compa- Oils of turpentine and lemon, and otto of 

rative compo- „ . #1 

aiftVu of es- roses, are examples of essential oils. They 
jtential oils ? are a i most as various as plants themselves. 
Yet the composition of those that differ most widely 
is often the same. This is the case with the oils of 
orange, lemon, pepper, turpentine, juniper, parsley, 
citron and bergamot. They contain carbon and hy- 
drogen alone, and in the same proportion ; twenty 
atoms of the former to eight of the latter. Those of 
bitter almonds, cinnamon, cloves and anise-seed con- 
tain oxygen beside. Those of mustard and onions, 
contain oxygen and sulphur in addition, and are char- 
acterized, like all sulphuretted oils, by a peculiar, pun- 
gent smell and acrid, burning taste. 

951. Occurrence and preparation. — 

How are the . . n . 

essential oils Essentials oils are oftenest found in the 
prepared? flowers, seeds, and fruits of plants, but 
sometimes in the stalks and roots. From these they 
are obtained by distillation with water. The volatile 
oil passes over with the steam, and floats upon the con- 
densed liquid in the receiver. Oil of turpentine is thus 
made from the common turpentine, or pitch as it is 
sometimes called, which exudes from the pine ; ordi- 
nary rosin remains behind. The delicate perfume of 
violets and other flowers which contain but a small 
portion of essential oil, is extracted by mingling the 
flowers with lard. This substance has the property of 
absorbing the oil and yielding it again by distillation. 



380 organic chemistry. 

952. Use of the essential oils. — 

What are the . . 

uses of the es- 1 he essential oils are extensively em- 
sentiai oils? ployed in the manufacture of essences, per- 
fumes and cordials. All of these liquids are solutions 
of the oils in alcohol, with the addition, in the case of 
cordials, of a portion of sugar. The oil of turpentine 
is used in the manufacture of varnishes and burning 
fluid, to be hereafter described. 

953. Burning fluid. — " Burning fluid, " 

What is the ■ . ° 

composition of so called, is a solution of camphene 01 
fluidr"^ rectified turpentine in alcohol. The sole 
object of the camphene is to increase the 
proportion of carbon, and thus render the flame more 
luminous. Unmixed camphene may also be burned in 
lamps provided with tall chimneys. The effect of the 
chimney is to make a strong draft, and thus provide a 
liberal supply of oxygen in proportion to the large 
amount of carbon which the liquid contains. With- 
out this provision, camphene burns like camphor, with 
much smoke, depositing a large part of its carbon in 
ti.e form of soot or lamp-black. 
roi * -o o -a 954. Burning fluid, " explosive." — 

What is said ' 

of the explo- The mixture of alcohol and camphene, 

sibility of . n ., . , 

"burning- known as burning fluid, is commonly 
fl uulr spoken of as explosive. That this is not 

the fact, may be readily shown by pouring a little in a 
saucer and inflaming it. It burns, under these 
circumstances, as quietly as from the wick of a 
lamp. But if a can, containing burning fluid, be 
shaken up and then emptied of its liquid con- 
tents, it is found to contain an explosive atmos- 
phere. To prove this, it may be tightly corked 



BURNING FLUID. 3S1 

and fired through a small hole punched in the side. On 
applying alighted taper to the opening, the can explodes 
with a loud report, and is torr. to pieces by the force 
of the escaping gases. The small proportion of fluid 
remaining in the can, after every drop that can be 
poured out is removed, is sufficient to produce this 
effect. 

955. Explanation. — The principle of 

What is tfie , . • ■ -11- , 

cause of the the explosion is precisely the same as that 
explosion. involved in the same experiment with hy- 
drogen and air. The only variation consists in the sub- 
stitution of the combustible vapor of alcohol and cara- 
pheue, for hydrogen gas. It is the mixture of alcohol 
vapor, and air, to which the effect is to be principally 
ascribed ; the experiment may be made, indeed, as 
well with unmixed alcohol, or ether, as with burning- 
fluid. It may also be made with camphene, but in this 
case the vessel must be warmed, in order to vaporize 
the liquid in sufficient quantity. 

956. The above experiment may be 

Describe an- r , . , r A . ■. -, 

other form of performed with safety, in an open vial, by 
the expen- vaporizing a drop or two of either of the 

me) d. r r 

above liquids within it, and then apply- 
ing a lighted taper to the mouth. In this case, the ap- 
pearance of flame at the mouth of the vial, and a 
rushing noise, is all that is observed. This experiment 
will enable the student to disprove the alleged unex- 
plosive character of certain fluids in use for purposes 
of illumination. In moderately warm weather it is 
sufficient to fill the vial, and then to empty it, in order 
to form the explosive atmosphere. 



3852 ORGANIC CHEMISTRY. 

957. Artificial essences. — Many of 

What is said . 

of artificial the essentials oils are compounds of organic 
acids and bases. Several of them may be 
artificially produced. Pine apple oil is a compound 
of butyric acid with ether or oxide of ethyl. The bu- 
tyric acid of the compound may be prepared from 
rancid butter or by fermenting sugaf with putrid 
cheese. Bergarnot pear oil is an alcoholic solution of 
acetates of the oxide of ethyl with acetate of oxide 
of amyl. The latter is the ether of the nauseous and 
poisonous fusel oil, which has before been mentioned. 

What is arti- 958 - A PP le oil is a compound of vale- 

ficial apple rianic acid with the same ether. The 

cial oil of bit- valerianic acid of the compound is also 

ter almonds? made from fugel &± Oil of grapes, and 

oil of cognac, used to impart the flavor of French 
brandy to common alcohol, come from th^ same source. 
Oil of winter-green may be prepared from willow bark 
and wood vinegar. Oil of bitter almonds is prepared 
from coal tar. These artifical essences, although pro- 
duced in several cases from poisonous substances, may 
be used as flavors with perfect safety. It is highly 
probable and in many cases certain, that the flavor of 
the fruits themselves, is owing to the presence of these 
precise compounds in small quantities. 

959. Empyreumatic oils. — -The vola- 

What are em- 
pyreumatic tile oils which are produced by the de- 
structive distillation of vegetable and ani- 
mal substances receive this general name. The oils 
of wood and coal tar are examples. Another em- 
pyreumatic oil is produced in the combustion of to- 



RESINS. 383 

bacco in ordinary pipes. This oil is extremely poison- 
ous. It is to be understood that these oils do not exist 
ready formed in the substances from which they are 
obtained, but are produced in the re-arrangement of 
atoms which takes place when organic bodies are sub- 
jected to a high temperature. 

960. Camphors. — Several of the oxy- 

What is the ■ ., . 

origin of the genated essential oils deposit white crystal- 
camphors? j^ ne so \[^ s by co ld. These are frequently 
isomeric with the oils themselves, and are called cam- 
phors. Ordinary gum camphor is obtained like the es- 
sential oils, by the distillation of the leaves of the Lau- 
ras Camphor i with water. Its volatile character is the 
occasion of a singular appearance when small bits of 
the substance are thrown upon warm water. The par- 
ticles are seen to sail about as if they were possessed 
of life, owing to the propelling effect of the vapor 
which escapes beneath them. 

How are re- 961 - Resins. — The resins, of which 

sins formed? ordinary pine rosin may serve as an exam- 
ple, are formed by the action of oxygen upon the essen- 
tial oils. Oil of turpentine may be thus partially con- 
verted into resin by long exposure to the air. On sub- 
sequently heating it, only a portion is found to be vola- 
tile, while a resinous mass remains behind. Turpen- 
tine, or pitch of pine trees, is thus formed in nature 
from the oil of turpentine as it exudes from the 
trees. But the conversion is only partial, so that the 
turpentine yields, on distillation, a portion of oil, while 
rosin remains behind. Resins are easily distinguished 
from gums by their insolubility in water ; they are, on 

17 



384 ORGANIC CHEMISTRY. 

the other hand, readily soluble in alcohol or ether. 
They are not liable to decay, like most other substan- 
ces of vegetable origin. Copal, shellac, mastic and 
amber are all resins. The latter is found in certain 
coal mines and at the bottom of the sea, and has 
probably had its origin in the forests of some primeval 
age. 

962. Explanation. — The action of 

Explain the . . 

aoove trans- the oxygen of the air in the above case 
j.rmation. ^ s i m ii ar to that which occurs in the con- 
version of alcohol into vinegar. A portion of the hy- 
drogen is burned out, as it were, and removed in the 
form of water, while another portion of oxygen takes 
its place. 
„ : . 963. Use of the resins — varnishes. — 

What use is 

made of the The resins are principally employed for the 

renns ? How , r . , mi . , 

are varnishes production oi varnishes. 1 hese are simply 
made? solutions of resins in alcohol, ether, or 

spirits of turpentine ; or an intimate mixture of the 
latter with fused resin and oil. In preparing copal var- 
nish, which is the most brilliant and durable, the resin 
is first fused, then incorporated with heated oil, and 
afterward diluted with spirits of turpentine. A com- 
mon varnish for maps, engravings, and similar objects, 
is made by dissolving mastic with a little Venice tur- 
pentine and camphor, in spirits of turpentine. Pounded 
glass is added to the pulverized material during the 
process of solution. The object is covered with a so- 
lution of isinglass before using this varnish, to prevent 
its absorption. Shellac, in alcohol, is employed to 
impart to wood or other material a resinous coating^ 



RESINS. 



3S5 



which is afterward polished with rotten stone. Copal 
varnish is also similarly used. Shellac, dissolved in 
soda or potash, is sometimes used to give body to 
paints, as a substitute for part of the more expensive 
material. 

Whatisrosin 964. Rosin soap. — The resins possess 
soap? an ac j(j character, and like fats, form soap 

with the alkalies. Common rosin is largely consumed, 
with fat and potash, in the manufacture of common 
brown soap. The greater hardness which it imparts 
depends on the formation of a certain portion of rosin 
soap in the mixture. 

965. Sizing. — The soap which is 

How is rosin 

used in sizing formed on boiling rosin with strong potash 
paper r ^ use( j j n s i z i o g paper. Being mixed with 

the material from which paper is to be made, a solution 
of alum is afterward added to the pulp, and a compound 
of rosin and alumina thus produced in every portion of 
the mass. The pores of paper made from this mate- 
rial are thus completely filled, and the spreading of 
the ink prevented. A surface sizing which is less ef- 
fectual, is also given to paper by a solution of glue, 
applied after the paper is formed. When this is de- 
stroyed by erasure, its place may be supplied, and the 
spreading of ink prevented by rubbing powdered rosin 
upon the spot from which the sizing has been removed. 
. , 966. Sealing-wax. — Sealing-wax con- 

What is the m & 

composition of sists, principally, of shellac. Venice tur- 
ing ' n pentine is added to make it more inflam- 

mable and fusible, and vermilion or lamp-black to color 

it. Ship pitch is resin changed and partially decom- 

17 




386 ORGANIC CHEMISTRY. 

posed by heat. Shoemaker ] s wax is made by a similar 
process. 

What are the 967 ' RoSIN 0IL AND GAS.— Rosin is 

products of partially converted by dry distilla- 

t/ie ary a/istxL~ , 

lation of tion into an oil, which is largely 

used for adulterating other oils, and 
also for purposes of illumination. A black pitch 
remains in the retort. The oil has the advan- 
tage of extreme cheapness, but owing to its 
large proportion of carbon, can only be burned 
in lamps furnished with tall chimneys. At a 
still higher temperature rosin is converted into 
gas, with a residue of carbon. 

What is as- ^68. AsPHALTUM. AsphaltUfll OX hi- 

phaltum? tamciL is a mineral resin, similar to the 
black pitch which remains from the distillation of coal 
tar. This material is found on the shores of the Dead 
Sea, in the island of Trinidad, and in several European 
localities. It is extensively employed for hydraulic 
cements, roofing, and pavements. 

969. Petroleum. — Petroleum is a liquid 

What is said 

of the source, hydrocarbon, also known as rock oil. It is 
7Uproper- often fomid u P on standing water, in bitu- 
ties ofpetrole- minous coal districts. Pits are also dug 
for the purpose of collecting it. These 
become filled with water, upon which the oil rises, more 
or less abundantly. The rectified petroleum is called 
naptha, and is a nearly colorless and highly volatile 
fluid. The entire absence of oxygen in its composi- 
tion, adapts it perfectly to the preservation of the metals 
potassium and sodium in their metallic condition. 



CAOUTCHOUC. 387 

It is also usod as a solvent of sulphur, phosphorus, fats, 
resins and caoutchouc. Both asphaltum and petroleum 
have been, probably, produced by the action of vol- 
canic fires upon bituminous coal. 

970. Gum resins. — The dried juices 

What is said . 

of gum re- of certain plants consist of mixtures of 
gum and resin. These mixtures are called 
gum resins. Water dissolves the gum, and holds the 
resin in suspension, thus forming what is called an 
emulsion. Alcohol, on the other hand extracts the re- 
sin from their mixtures. Assafoetida, gamboge and 
opium are a few examples of gum resins. 

971. Caoutchouc Gum elastic, — 

Mention the -it • 

sources and Caoutchouc is a hydrocarbon obtained from 

V Ja?utlouc f the milk y J uice ° f certain treeS in Asia > 

Africa and South America. This constit- 
uent of the juice hardens on exposure to the air, while 
the remainder is removed by evaporation. By the ad- 
dition of a little ammonia, the milk may be retained in 
its liquid condition. Caoutchouc is soluble in ether, 
spirits of turpentine, oil of coal tar, and many other 
hydrocarbons. Sulphuret of carbon, a volatile liquid 
obtained by passing sulphur vapors over ignited char- 
coal, is also a complete solvent of India-rubber and 
gutta percha. 

972. Vulcanized rubber. — Heated for 

How is caout- , . . , , , nnAO 

chouc vulcani- a snort time with sulphur, at zo(J , or 
zed? What some what above this point, caoutchouc 

are the prop- r ; 

ertiesof vul- becomes remarkably changed in its nature, 
her?" an d is no longer stiffened by cold or soft- 

ened by heat. It is then called vulcanized 



388 ORGANIC CHEMISTRY. 

rubber, and constitutes the material out of which 
most India-rubber goods are now made. The hard 
rubber which is extensively emplojred for the manu- 
facture of combs, knife-handles, pencil-cases, &c, is 
composed of pitch, India-rubber, sulphur, and mag- 
nesia. The mixture is softened at about 270°, then 
pressed into moulds to give it the required shape. It 
is afterward wrought like ivory. 

Whatisgutta 973 - Gutta percha.— Gutta percha is 
percha? identical in composition with gum elastic, 

Mention some m 

of its proper- but possessed of quite different properties. 
ties an uses. Among them is its extreme toughness and 
comparatively slight elasticity. It is rendered soft and 
plastic by immersion in boiling water, and in this pasty 
condition may be moulded into any required shape. It 
can be vulcanized, like caoutchouc, and is then proof 
against elevation of temperature. It is employed as a 
substitute for caoutchouc where great elasticity is not 
required. Both of the above substances approach more 
nearly in their composition to the essential oils than to 
any other class of compounds. 



PROTEIN BODIES— PUTREFACTION. 
a . . ,, 974. Vegetable fibrin. — The glutin- 

State the com- ° 

position and us mass which remains when dough is 

properties of . . 

vegetable kneaded in water until all the starch is 

fibrw, removed, is called gluten or vegetable 

fibrin. It differs from all the organic matter hitherto 
described, in containing nitrogen, with small quantities 



VEGETABLE ALBUMEN. 



389 



of sulphur and phosphorus. Its exact composition is 
given in the Appendix. It is a grey substance, and is 
the material which gives its cohesion to bread. 

975. Vegetable albumen and casein. — 

Tv hat zs said 

of vegetable Vegetable albumen is a similar substance, 
albumen and con t a ined, in smaller quantity, in the juices 
of fruits and vegetables. It is coagulated 
by heat, like the white of egg, when the juices are 
boiled. Vegetable casein is another substance of very 
similar composition and properties, found principally 
in the seeds of leguminous plants. It precipitates like 
the curd in sour milk, when a little acid is added to 
an aqueous extract of the seeds. These substances 
derive their names from their resemblance to animal 
fibrin, albumen, and casein. Vegetable casein is also 
called legumine. All of these substances were at one 
time supposed to be compounds of a single substance, 
called protein, itself free from both sulphur and phos- 
phorus. Later experimenters have not succeeded in 
isolating such a substance, and the theory is therefore 
abandoned. The name is retained in this work as a 
convenient designation of the class of substances here 
considered. 

976. Occurrence. — One or more of 

M here are the 

above substan- these substances is present in greater or 

ces found? legs quantity in all parts f plantSi They 

are found accumulated with starch, in the fruit and 
seed. The seeds of cereals, such as wheat and rye, 
and those of leguminous plants, such as peas and beans, 
contain them in large proportion. 



390 ORGANIC CHEMISTRY. 

Mention ape- 977 ' CHARACTERISTICS.— If a bit of 

culiarltj/ of gluten be placed on the end of a wire and 

these nitro~ 

genous com- burned, a very different odor is produced 
pounds. £ rom that of burning starch or wood. 

The smell approaches that of burning wool, and is a 
means of distinguishing organic matter which contains 
nitrogen. If boiled with potassa, the sulphur of gluten 
is extracted, and the solution will blacken paper moist- 
ened with sugar of lead. This reaction furnishes an- 
other means of detecting these nitrogenous substances. 

978. Putrefaction. — A still more im- 

Describe the 

process of pu- portant distinction of nitrogenous substan- 
trpfacuon. ceg f rom those which contain no nitrogen, 
is their spontaneous putrefaction. Left to themselves, 
they are resolved, like blood and flesh to which they 
are allied in composition, into a variety of other pro- 
ducts. It is not strictly correct to say that this decom- 
position is spontaneous. The substance must first 
have been exposed to the air. An oxidation or slow 
combustion is then commenced, which, although en- 
tirely imperceptible in its effects, and checked at once 
by exclusion of air, ensures the subsequent putrefac- 
tion. It burns out a small portion of carbon and hy- 
drogen, and thus removes, as it were, the key-stone of 
the arch in every molecule. The atoms may then be 
supposed to fall together and re-arrange themselves as 
is required by the known products of their decompo- 
sition. 

979. Products of putrefaction. — The 

j&iention some 

products of re-arrangement which occurs in putrefac- 
pu re/action. i[ on ^ cons j s t s? essentially, in the combustion 



FERMENTATION. 391 

of the carbon of the substance with oxygen, while the 
hydrogen divides itself between the nitrogen, phospho- 
rus and sulphur, forming ammonia, phosphuretted and 
sulphuretted hydrogen. It is to these gases that the 
offensive smell which is given off in putrefaction is 
principally to be ascribed. 

980. Fermentation. — Any one of the 

WJiat sub start- . . 

cesare capable nitrogenous substances above mentioned, 
of producing w hii e undergoing the change which is 

fermentation f o o o 

called putrefaction, is capable, by its mere 
presence, of acting as a ferment. A little putrefying 
gluten, for example, added to a solution of sugar, will 
convert it into alcohol and carbonic acid. Here again 
the key-stone of the molecule is removed, or rather in 
this case moved. The motion of the atoms of the 
putrefying substance would seem to be the cause. 
The effect is analogous to that of heat, through whose 
agency, also, complex organic bodies are resolved into 
others of simpler constitution. 
TTr7 . 7 981. Yeast. — The first stage in the 

What is the & 

first stage in formation of yeast is the production of a 
e pro ?ss. microscopic vegetation, which consumes 
all the protein, converting it into the substance of a 
microscopic plant. Ordinary brewers' yeast is such a mi- 
croscopic vegetation. Being produced, it passes imme- 
diately into the putrefaction above described, effecting, 
at the same time, the conversion of any sugar which 
may be present into alcohol and carbonic acid. By 
some, the growth of the microscopic plant itself, instead 
of its subsequent change, is supposed to be the cause 
of fermentation. 



392 ORGANIC CHEMISTRY. 

How is yeast 982. PRODUCTION OF YEAST. Yeast has 

produced? not on jy t i le p 0Wer f converting sugar 
into alcohol, but it at the same time occasions the 
production of more yeast from dissolved protein. In 
the ordinary process of beer brewing, the newly formed 
yeast collects on the surface of the fermenting vats. 
It is thence removed, to serve as the excitant of a new 
fermentation, or to be employed in the production of 
bread, which is, chemically considered, an analogous 
process. 
,^ ,. 983. Different kinds of fermenta- 

Mcntion seve- 
ral kinds of tion. — The products of fermentation are 
fermentation. different? according to temperature and 
other circumstances. Thus the same sugar which at 
40° to 86°, with cheese used as a ferment, yields car- 
bonic acid and alcohol, at a temperature of 86° to 95° 
is converted into lactic acid. The latter, by the further 
action of the curd, with slight elevation of tempera- 
ture, is converted into butyric and carbonic acids. By 
the same ferment, at a still higher temperature, a portion 
of gum is produced with the lactic acid. These diffe- 
rent processes of transformation have received, respec- 
tively, the names of the vinous, lactic, butyric, and 
viscous fermentations. The conversion of starch into 
sugar by diastase may be regarded as a species of fer- 
mentation. This substance is a slightly changed glu- 
ten. It is always produced in germination, and may 
be precipitated by alcohol in the form of white tiaKes 
from a concentrated infusion of malt. One part of it 
is sufficient to convert two thousand parte of starch 
into sugar. 



BREAD. 393 

mat is said 984 ' Flour.— Fine flour makes less 

of the nutri- nutritious bread than the coarser varieties, 

iious proper- . . . 

ties of fine because it contains a smaller proportion of 
fl our ' gluten. Gluten being tougher than the 

starch, is not reduced to so fine a powder and is par- 
tially separated in the process of bolting. All grains 
contain sugar in small proportion. Sugar is therefore 
one of the constituents of flour. 

What chemi- $85- Bread. — The " raising " of bread 

cai principles j s a process of fermentation. The yeast 

are involved . . 

in making employed in the process converts a portion 
bread? Q f the starc h f ^q q oux i nt0 SU g ar? and 

subsequently into alcohol and carbonic acid. The 
sponge is made light and porous by the gas bubbles 
which become entangled within it. A large part of 
the alcohol produced in the process escapes into the 
oven, and thence into the exterior air. It may be 
condensed and converted into spiiHts by the proper 
apparatus. This has been successfully done in large 
bakeries in Europe, but the process has not been found 
to be of any considerable economical importance. In 
baking a small portion of starch is always converted 
into gum. By moistening the baked loaf with water 
the gum is dissolved, and by a new heating, hardens 
into the shining surface which is often observed on 
bakers' bread. 

What materi- 986 « YeAST POWDERS.— The gas which 

ah are some- i s needed to make bread light, may be 

times substi- 
tuted for produced by other means than the process 

yeast ? Q f f ermen tation. If carbonate of soda, for 

example, is kneaded into the dough, and tartaric acid 
17* 



394 



ORGANIC CHEMISTRY. 



subsequent y added in proper proportion, the weaker 
carbonic acid is expelled. A light sponge is produced 
by its escape, without the loss of the starch and sugar 
which are consumed in the process of fermentation. 
Soda and tartaric acid prepared for this purpose are 
known under the name of yeast powders. Carbonate 
of ammonia being entirely volatile by heat, may be 
employed alone for the same purpose. A portion of 
the salt probably remains in the bread, and is more 01 
less injurious on account of its alkaline character. 

987. Test for yeast powders. — The 

What is the ... 

objection to great objection to the use of these pow- 

&c U infre S ad7 ^ ers in the P re P arat i ori °f bread, consists 
in their liability to contain soda or acid in 
undue proportion. Whether this is the case, may be 
ascertained by dissolving the powders in water and 
mixing the solutions. If the product is neutral to the 
taste and does not effervesce on the addition of 
either soda or acid, this fact will be evidence of their 
proper preparation. If otherwise, more or less injury 
is to be anticipated from their use. Excess of the al- 
kalies especially interferes with the process of diges- 
tion, by neutralizing the acids which accomplish it. 
The use of soda and saleratus with sour milk is liable 
to the same objections. 

What is said, 988- THEIR EFFECT ON HEALTH. It 

in addition, of may we ^ ^ Q q lles tioned whether bread 

their effect on J * 

the health? prepared by this process is ever as healthy 
as that made with yeast. For even the neutral tar- 
trate, formed when the materials are used in proper pro- 
portion, will tend to neutralize certain stronger acids 



ALKALOIDS. 395 

which are constituents of the gastric juice. It may 
thus interfere, in a measure, with the process of diges- 
tion. If pure muriatic acid were substituted for the 
tartaric acid or cream of tartar, this objection would be 
removed. The product of its action on soda is com- 
mon salt. 

ORGANIC BASES. 

989. Alkaloids. — Morphine and strych- 
namesofsome nine, the former a useful medicine, and 
ioids "why the latter ? the most dreadful of poisons, are 
.re they so examples of the alkaloids. They are 
white crystalline bodies but slightly solu- 
ble in water. Most of them, like the protein bodies 
above mentioned, contain the four organic elements ; 
but they differ widely from these substances, in possess- 
ing a positive chemical character. They are called 
alkaloids from their resemblance, in certain properties, 
to the alkalies of inorganic chemistry. Their action 
upon vegetable colors is the same ; like the alkalies, 
they also form salts with both organic and inorganic 
acids. They are, in fact, true alkalies. Their alkaline 
property does not, however, seem to depend on the 
oxygen which they contain. Some of them, indeed, 
do not contain this element. It is highly probable that 
certain of the alkaloids belong to the class of compound 
ammonias mentioned in the first chapter of Organic 
Chemistry. 

What is their ^90. Their action on the human body 
action on the (joes not depend upon their alkaline char- 

human body f . 

Their anti- acter, but on other and peculiar properties 
belonging to each. The salts of the alka- 



396 ORGANIC CHEMISTRY. 

loids are generally preferred in medicine, in view of 
their ready solubility. In large doses they are all 
poisonous. The tincture of nut-galls is employed as 
an antidote, because of the property of the tannic acid 
which it contains, to form with most of the alkaloids 
insoluble precipitates. 

991. Occurrence. — Morphine is con- 

What is the . . ... 

source of the tamed in opium, quinine is extracted from 
alkaloids? Peruvian bark, and strychnine from the mix 
vomica. The latter is also the poison of the celebrated 
upas. Theine and nicotine are other alkaloids, the 
former of which is found in tea and coffee, and the latter 
in tobacco. Theine may be obtained, as a sublimate 
of silky crystals, by moderately heating tea in an iron 
pot covered with a paper cone. 

992. Preparation. — Most of the alka- 
aikaloids ex- loids may be extracted from the material 
traded? which contains them by means of acidu- 
lated water. A salt of the alkaloid is thus obtained in 
solution. From this salt the alkaloid may be precipi- 
tated, like oxide of iron or any other base, by am- 
monia. Nicotine is a most energetic poison, falling 
scarcely below prussic acid in its destructive properties. 

COLORING MATTERS. 

What is said " 3 - Indigo.— The vegetable dye-stuffs 
of indigo? are extremely numerous. Indigo, madder, 
and logwood are among the more important. Indigo 
is deposited from the colorless juice of certain plants 
by simple exposure to the air. It may be sublimed in 



DYEING. 397 

purple crystals by rapid heating. By removing the 
oxygen absorbed in its production, the original color- 
less juice may be. as it were, reproduced from commer- 
cial indigo. This object is effected by the use of pro- 
tosulphate of iron, which is converted into sulphate of 
the peroxide in the process. Caustic lime is at the 
same time added to dissolve the deoxidized indigo. 
The colorless solution is employed in dyeing : cloth im- 
pregnated with it becomes blue on exposure to the 
air. A solution of indigo in concentrated sulphuric 
acid is also employed in dyeing. 

What is mad- 994. Madder. — Madder is the ground 
der? root of the rubia tinctorium. This plant 

is cultivated extensively in India and Europe. It con- 
tains a red dye, produced by the action of the air or 
certain chemical agents upon the juices of the recent 
plant. This body is called alizarine and may be ob- 
tained in beautiful crystals. An infusion of the root in 
hot water contains a portion of this substance in solution. 
What is log- 99-5. Logwood. — This is a red wood, 

wood? obtained from Spanish America and much 

employed in dyeing. Its coloring matter is called he- 
matoxylins. By evaporating a decoction of the wood 
and re-dissolving in alcohol, this substance may be ob- 
tained, on a second evaporation in the form of yellow 
crystals. 

DYEING. 

996. Dyeing. — Few dyes can be per- 

Explain the 

theory of dye- manently imparted to cloth without the m- 
mg fast colors. tervent i on f some third substance, which 



398 ORGANIC CHEMISTRY. 

shall, as it were, hold them together. Such a substance, 
with strong affinity for the coloring matter of the dye 
and also for the fibre of the cloth, is called a mor- 
dant. The fabric to be dyed being first impregnated 
with the mordant, is then introduced into the dyer's 
vat to receive its permanent color. 
What is said 997. Mordants. — Alumina and oxide of 
*>/ mordants? j ron are t } le principal mordants employed. 
They may be " fixed " in the cloth by immersion in the 
acetates of these oxides. A subsequent exposure for 
several days to the air is essential, in order that the 
acetic acid may in part be expelled. A portion of it, 
however, remains, so that the oxides are, strictly speak- 
ing, in the condition of basic acetates. After this ex- 
posure, and subsequent washing in hot water, the fabric 
may be immersed in the dye. An ounce of madder 
heated with a pint of water will be sufficient for an 
experiment. The fabric is to be boiled for an hour or 
more with the unstrained decoction. 

998. Preparation of the mordant. — 

How is the alu- «,.''. n n . . 

minousmor- The solution of acetate of alumina is 
^arcd? 6 ' most conveniently prepared from alum, by 

the substitution of acetic for its sulphuric 
acid. This is accomplished by the addition of acetate 
of lead. Sulphate of lead is at the same time precipi- 
tated, and may be filtered off from the acetate which is 
formed. Three pounds of alum and two of sugar of 
lead, to three gallons of water, are the proportions to 
be employed. This mordant produces a red color. 

How are vari- 999. VARIOUS COLORS BY THE SAME 

ous colors pro- DYE — g y t h e use of different mordants, 

aucedfrom one * 

dytt various colors may be produced from the 



MINERAL DYES 399 

same dye. Substitute four pounds of green vitriol for 
the alum used in the previous case, and the madder 
gives a deep black. Add four ounces of arsenic with 
the green vitriol, and a mordant is produced with which 
the dye will yield a beautiful purple. In the latter 
case, the solution must be reduced to one-tenth of its 
original strength by the addition of water. 

1000. Dyeing with logwood. — By the 
briefly the pro- employment of the last two mordants, 
ZVfo/Zodf mixed in equal proportions and diluted to 
half their strength b y water, a mordant for 
dyeing black with logwood is obtained. For dyeing 
purple with the same material, a tin mordant is used. 
It may be prepared by dissolving tin in muriatic acid 
with the gradual addition of nitric acid, then precipi- 
tating and re-dissolving with potassa. The cloth being 
impregnated with this mordant and thoroughly dried, 
is passed through dilute sulphuric acid, to remove the 
potassa and leave the oxide of tin. After subsequent 
drying and exposure to the air, the fabric is ready for 
the dye. 

What are 1001. Mineral byes. — The dyes de- 

mmeral dyes? scr j D ed i n the following paragraphs, are 
distinguished from those before mentioned by contain- 
ing no organic matter. They consist of colored salts or 
oxides precipitated in the fibre of the cloth. Although 
these substances belong, strictly speaking, to inorganic 
chemistry, they are here introduced to complete ih» 
survey of the subject of dyeing and calico printing. 
TT . . 1002. Prussian blue. — A mineral blue 

How is a min- 
eral blue ob- may be produced by impregnating cloth 

with the solution of acetate of iron, before 



400 ORGANIC CHEMISTRY. 

described as a mordant, and then immersing it in an 
acidified solution of prussiate of potash. Prussian blue 
is thus precipitated in the cloth. This blue is found to 
be brightened by passing it through a solution of sugar 
of lead. 

1003. Mineral green. — A mineral green 

How is a min- . 

eral green pro- is produced in the same manner by the em- 
ducedi ployment of sesquichloride of chromium, 

and subsequent immersion in potassa. The color con- 
sists of sesquioxide of chromium, precipitated from the 
chromium salt by the action of the alkali. The so- 
lution of sesquioxide of chromium is prepared by the 
addition of sugar to a solution of bichromate of potassa 
in dilute sulphuric acid. A part of the oxygen of the 
chromic acid being abstracted by the organic matter, it 
is converted into an oxide, which remains in solution. 

1004. Chrome yellow. — To produce a 

How is a min- . . 

eral yellow mineral yellow, the cloth may be lmpreg- 
produced? na ted with acetate or nitrate of lead, then 
dried and passed through sulphate of soda, to fix the 
lead as sulphate in the cloth. On finally immersing 
it in bichromate of potassa, the cloth becomes dyed 
with yellow chromate of lead. The above process 
modified by printing instead of saturating with acetate 
of lead, gives yellow figures on a white ground. 

CALICO PRINTING. 

Howisawhite 1005. White figures.— If it is desired 
design on dyed t0 obtain a design in white, on goods dyed 

goods j>ro- ° 

duced? with either of the above madder colors, 




CALICO PRINTING. 401 

the design is printed with a 
paste of tartaric acid upon the 
colored cloth. On subsequently 
immersing the goods in a bath 
of chloride of lime, chlorine is evolved in the tissue, 
and the color discharged only where the acid is printed. 
The white thus produced is of course in exact cor- 
respondence with the printed design. 

Eowareyellow 1006 ' Pmnted YELLOW AND BLUE.— To 

and blue de- produce yellows on madder red and purple 

signs obtained 

on dyed grounds, before described, tartaric acid is 

grounds? p r i nte d with the nitrate of lead, and the 

cloth immersed in bleaching liquid. The color of the 
printed portions is discharged by the combined action 
of the acid and bleaching liquor ; the lead is at the 
same time fixed in the cloth as chloride of lead. On 
subsequent immersion in bichromate of potassa, the 
yellow figures of chromate of lead are produced as be- 
fore. For blues on the same colored grounds, a mix- 
ture of Prussian blue, dissolved in bichloride of tin, 
with tartaric acid, is printed on the cloth. The dis- 
charge of the ground color beneath the figure^ is 
effected, as before, by chloride of lime. 

1007. Variegated patterns. — All of 

How are varie- . 

gated patterns the madder colors which have been men- 
produccdi tioned, may be produced upon a single piece 
of white goods, by printing the different figures of the 
pattern with different mordants. This is accomplished 
by passing the fabric between different sets of rollers, 
each of which is supplied with a paste of the proper 
mordant, and so engraved that it yields the desired im- 



402 



ORGANIC CHEMISTRY. 



pression. On subsequently introducing the goods into 
the madder bath, the various colors are developed. The 
whole piece is at the same time transiently colored ; 
but the dye may be readily removed from the unprinted 
portion by thorough washing. A white ground for the 
colors is thus obtained. 

RELATION OF PLANTS TO THE SOIL. 

AGRICULTURAL CHEMISTRY. 

1008. The mineral substances which 

Whatmineral , , A . r , ., , .. 

substances do plants obtain from the soil, are known by 
plants obtam aIia lysis of the ashes which they yield on 

from the soil * . 

combustion. They consist of acids and 
bases, which enter into the composition of all fertile 
soils. The bases are potassa, lime, magnesia and 
oxides of manganese and iron. These are found com- 
bined in the ashes with silicic, sulphuric and phosphoric 
acids, and are accompanied by small proportions of 
common salt. The carbonic acid which is found in 
certain ashes is produced in the combustion of the 
plant. The ashes of all cultivated plants contain the 
above substances ; but in different proportions accord- 
ing to the nature of the plant. The phosphates pre- 
dominate in grains ; lime exists in large proportion in 
grasses ; potash in edible roots ; and silica in straw. The 
approximate composition of the ash of different plants 
is given in a table in the Appendix. In estimating the 
relative proportions of the different constituents which 
are abstracted from the soil by different crops, the quan- 
tity of the crop, as well as the composition of its ash, 
is of course to be brought into this account. 



CONSTITUENTS OF SOILS. 403 

1009. Composition of soils. — Many of 

Of what are . 

tolls com the above substances are contained in the 

pos soil in extremely small proportion. Soils 

are principally composed of vegetable matter in a state 
of decay, with clay, sand and carbonate of lime. The 
vegetable matter consists of the remains of plants of 
previous years, and the clay, lime and sand are the 
product of the gradual crumbling and decomposition 
of the rocky crust of the earth. 

1010. Use of vegetable matter in 

State t/te uses 

of vegetable soils. — The wood, leaves and twigs of 
"lllT m which vegetable matter is composed, fur- 

nish, in their gradual decay, the potash, 
silica, and other constituents of their own skeletons to 
form the framework of new plants. The organic mat- 
ter is at the same time converted into ammonia and 
carbonic acid ; these constitute the gaseous food on 
which all vegetable life is sustained. 

1011. Addition of vegetable and ani- 
^t;i "al M A T TE K._The addition of more of 
by the addi- this material to the soil, in the form of peat 

Hon of v eg eta- „ , 

ble and animal or muck from swamps, is of great advan- 
Tofll7 t0 ta § e > because it increases the supply of the 

two important classes of materials which 
have been mentioned. Animal matter of all kinds, 
whether decomposed, as in stable manure and guano, 
or in its original condition in the form of flesh, wool, 
and bones, is a still more valuable addition to the soil. 
The reason of its higher value, consists in the fact 
that while it yields most of the other substances which 
decaying vegetable matter supplies, it furnishes ammo- 



404 ORGANIC CHEMISTRY. 

nia, which is the rarest and most expensive one, in 
much larger proportion. 

1012. Use of the clay. — The clay in 

What purpose . . 

does clay sub- soils serves to retain the ammonia and 
serve in the certain other valuable materials, which 

son f 7 

would, otherwise, be washed away by 
descending rains. It seizes not only upon that which 
comes from the decaying humus, but finds particles in 
the drops of every shower, which it stores safely away 
for the future use of the plant. It serves also to retain 
moisture in the soil, and to impart to it the tenacity 
by which the roots are enabled to gain a firm hold upon 
the earth. Soils which contain but a small proportion 
of clay are for these reasons improved by its addition. 

1013. Uses of the sand. — Sand 5 where 

What is the 

office of sand it exists in due proportion, gives the proper 
m soils! degree of porosity to the' soil, and thus 

ensures the entrance of the air and fertilizing liquids, 
and the draining away of all excess of water. Access 
of air is important, because it brings with it fertilizing 
ammonia and carbonic acid, and by accelerating the 
decay of vegetable matter, produces more of these 
valuable substances. 

1014. Uses of the lime. — The lime in 
office of lime soils, beside serving directly as building 
on the soil ? material for all forms of vegetation, is the 
key which unlocks other treasures of the soil and sup- 
plies them, also, to the growing plant. The building 
material which is furnished, as before explained, by 
the decay of previous plants, is not sufficient. A por- 
tion of it never reaches the fields from which it was 



ACTION OF LIME. 405 

originally derived. Exported in the form of grain, or 
milk, or beef, it returns to the soil in some distant re- 
gion or is poured into the rivers and the sea through 
the drains of populous cities. New supplies of potash 
and other material, are, therefore, demanded by the 
vegetation of every successive year. 

1015. A large part of the materials re- 

How does it t . 

accomplish the ferred to are locked up in hard grains of 
Ject ' granite or other silicates which are found 

in the soils. Being insoluble in water and the other 
solvents of the soil, they are inaccessible to the plant. 
Lime has the property of forcing itself into the rocky 
prison of every such insoluble grain, and setting part 
of its inmates at liberty. At the same time it opens 
the door to the action of other agencies which liberate 
the rest. They are then floated away in the water 
which penetrates the soil, and being in due season ab- 
sorbed, are built into the substance of the plant. 

. 1016. Action OF LIME OX MINERAL MATTER 

Give the chem- 
ical explana- explained. — The action of lime, which 

lion l S aC ~ ^ as J ust been mentioned, is a simple conse- 
quence of its basic properties. It takes 
possession of part of the silicic acid of the alkaline 
silicate in the rocky grains. Their potassa and soda 
being now combined with this acid in small proportion, 
are soluble in the water which penetrates the soil. 

10 i 7. The water of the soil always con- 

What other . . • /- n •' • i 

decomposing tains a certain proportion 01 carbonic acici. 

agent exists in This acid being itself material for vege- 

table nutrition, has also the property of 

dissolving those mineral substances which the plant 



406 ORGANIC CHEMISTRY. 

needs for its support. By the joint action of carbonic 
acid and water, this transfer is constantly going on 
even without the aid of lime. But the latter substance 
very much accelerates the action, and thus adds greatly 
to the fertility of the soil. 

1018. Action of lime on organic mat 

Mention an- ■ . . 

other use of ter. — Lime has another important enecl 
l soU 0nthe on so ^ s ? i n hastening the decomposition 
of their organic matter, and thus, indi. 
rectly, supplying in large quantity, valuable materials, 
before mentioned, which these are adapted to furnish 
As this decomposition proceeds in the presence of lime, 
part of the nitrogen of the organic matter takes the form 
of ammonia, and part is converted into nitrates, as will 
be remembered from the chapter on Salts. But the 
proportion of either is practically immaterial, as both 
are found to subserve a similar purpose in building up 
the plant. 

1019. All of the efTects which have 
abZemm 6 t> een mentioned, may be regarded as grad- 
tioned effects ually produced in every soil which contains 

increased ? 

Mention an- carbonate of lime as a constituent. When 
Ume reffeCt ° f it; is deficient in quantity, they are, of 
course, increased by its addition in the 
form of chalk or marl or limestone. These substances 
have also the effect of sweetening peaty and marshy 
soils, which are rendered sour from the presence of too 
large a proportion of vegetable matter, and thus ren- 
dering them fit for cultivation. 

1020. Burned lime. — Burned or caustic 

In what form _. _ ... /Y> . . 

has lime the lime has all these effects in a much greater 

g fect? 8t ^ degree, and therefore its extensive use as 

a fertilizer of the soil. It shoulcj be used 



GUANO. 407 

cautiously on soils which contain but a small propor- 
tion of vegetable matter, for fear that in the more rapid 
decomposition which it stimulates, it may entirely 
exhaust the soil of this material. If employed in such 
cases it should be with admixture of vegetable matter, 
that the loss which it occasions may be completely 
replaced. 

1021. Effect of ashes on soils. — 

What other 

substances act Potassa or soda applied in the caustic state, 
wtaTllltion or as carbonates, have entirely analogous 
is to be observ- effects on the soil. They render the in- 

edin their use? . 

soluble silicates soluble, by increasing in 
them the proportion of base, and also hasten the decay 
and conversion of vegetable matter. The admixture 
of lime or ashes with guano or decomposed manure is 
to be avoided, because of their effect to expel the 
ammonia which these substances contain. This may 
be prevented by previously incorporating the material 
with a large proportion of clay or vegetable mould, 
which shall serve as an absorbent of the liberated 
gas. 

Wliat is said 1022. COMPOSTS. CoilipOStS Consist of 

of composts I vegetable and other matter, heaped to- 
gether for fermentation and partial decay in order to 
prepare them for application to the soil. In such mix- 
tures, all alkaline materials, including lime, have an 
effect similar to that which they produce upon the 
organic matter of the soil. 

Wliat is gua- 1023. Guano. — Guano consists of the 
nof accumulated droppings of birds, and is 

principally obtained from certain rocky islands on the 

16 



408 ORGANIC CHEMISTRY. 

coast of South America. In these haunts of the heron 
flamand, and other sea-fowl, it is accumulated, in some 
instances, to the depth of a hundred feet. The de- 
posit is usually in smaller quantity, but amounts in the 
aggregate to millions of tons. The material was em- 
ployed as a fertilizer by the natives of Peru and Chili, 
long before its introduction into England or the United 
States for the same purpose. 

1024. Different VARiETiEs.-The qual- 

M 'hat is said . „ 1>rr , . ., _. 

o/ different ity of guano diners materially, according 
varieties of t0 foe source from which it is derived. 

guano f 

The ammoniacal salts, on which its agency 
as a fertilizer principally depends, being soluble in 
water, the product of moist climates is of comparatively 
little value. The best is obtained from the coast of 
Peru, where rain seldom or never falls. The African, 
Patagonian and other varieties are much inferior. 

On what does 1025 ' AGRICULTURAL VALUE.— The ag- 

theagricuU ricultural value of guano lies principally 

tural value 

of guana in the ammonia and phosphate of lime 

depend? which it is capable of yielding to plants. 

These constitute, in the best varieties, about one-third 
of the whole weight. Part of the ammonia is ready 
formed, and part is produced in the subsequent change 
which the nitrogenous matter of the guano experiences 
in the soil. The latter may be produced immediately 
by a chemical process, and its quantity accurately 
determined. In estimating the value of guano, it is 
customary to record the quantity of this potential am* 
monia, as if it were an existing constituent. 



soils. 409 

What is said 1026 - Artificial ammonia.— The con- 

of the artifi- stituents of the ammonia which we pur- 

cial produc- , „ r 

Hon of ammo- chase in the form of guano at so great 
ma - expense and bring from distant regions of 

the earth, exist in unlimited quantity at our very 
doors. Four-fifths of the atmosphere are nitrogen gas, 
and the ocean is an exhaustless reservoir of hydrogen. 
But, strange to say, the chemist with all his skill, 
cannot, except by circuitous and expensive methods, 
effect their combination. The discovery of some cheap 
and ready means of accomplishing this object, would 
transform the face of the earth, by the unlimited quan- 
tity of fertilizing material which it would supply. This 
result may, perhaps, be reached by patient investiga- 
tion. But no sudden triumph over nature need be 
anticipated. Improvements in Agriculture will, as a 
general thing, be only realized by the earnest co-opera- 
tion of scientific and practical men, in laborious and 
oft-repeated experiment. 

1027. Exhaustion of soils. — When 

What is said 

oftheexhaus- soils become exhausted of those substances 

turn of soils? which f()rm the mineml f 00( J of plants? the 

growth of vegetation ceases. It is never absolute, 
but consists in a great reduction «f that portion of 
their material which is in a condition to be appropri- 
ated by the growing plant. Such soils are gradually 
restored by rest. A gradual decomposition of their 
insoluble material occurs by means of agencies which 
have before been mentioned, and the soil is thus re- 
stored to its original condition. These effects are very 
much hastened by plowing in such a growth as can 

IS 



410 ORGANIC CHEMISTRY. 

be obtained. Rye, buckwheat, and clover are among 
the plants best adapted to the purpose. Vegetable mat- 
ter is thus added to the soil, which, in its decay, hastens 
the decomposition of the soil itself. 

What is said 1028. DEFICIENCY OF ONE OR MORE CON- 

of deficient stituents. — The comparative exhaustion 

cies in partic- 
ular constitu- of some one or more of the constituents 

of the soil is a much more frequent oc- 
currence. It is commonly the result of the cultiva- 
tion of the same crop during many successive seasons, 
and the consequent reduction of those materials which 
the particular plant requires in largest proportion. De- 
terioration of soils from this cause is repaired by an 
artificial supply of the failing ingredients. It is more 
wisely guarded against by such a rotation of crops as 
shall make different demands upon the soil in succes- 
sive years. 

What is said 1029 - Maintenance of fertility.— 

of the effect of The effect of decomposing animal matters 

decomposing . ' - ■■ j 

animal matter on the soil has been already considered. 
%n the soil ? They return the very material which was 
abstracted from the soil, with the addition of nitro- 
genous matter originally derived from the air by the 
growing plant. In an enlightened system of rural 
economy, the production of these materials in large 
quantity and their careful preservation, is therefore an 
object of paramount importance. The addition of 
gypsum or dilute sulphuric acid to fermenting ma- 
nures, is of great advantage in retaining .their ammonia 
in the form of sulphate and preventing its escape into 
the air. When additional ammonia is required, i* is 



" SUPERPHOSPHATE. " 411 

most cheaply obtained in the form of guano. The 
phosphates, whose quantity may be often increased 
with advantage, are best supplied in the form of " super- 
phosphate of lime." Other materials are less frequently 
required. For further information on the subject of 
the present section, the student is referred to works 
which treat especially of Agricultural Chemistry. 
TTr7 . ■ 1030. " Superphosphate of lime." — 

What is said . 

of mperphos- 1 he method employed in the manufacture 
phateofiime? of « supe rphosphate of lime," has been al- 
ready given in the chapter on Salts. As in the case 
of guano, its agricultural value depends on actual or 
potential ammonia and phosphate of lime. In propor- 
tion as the phosphoric acid is in a soluble form, the 
value is much increased. Additional information on 
this subject is given in the Appendix. 



ANIMAL CHEMISTRY. 



CHAPTEE III. 



ANIMAL NUTRITION. 



1031. Relations of animal and vege- 

How is the . * . • 

life of ani- table life. — The life of animals IS sus- 
mah sustain- ta i ne( j by t h e consumption of material 

compounded and prepared by the plant, 
and converted into its own substance out of the mate- 
rials of the earth and air. This is virtually true even 
of the carniverous species, for the animals on which 
they feed have derived their support from the vege- 
table world. When they yield their own flesh as food, 
it is only a changed vegetable matter which they thus 
supply. All animal matter may therefore be regarded 
as vegetable matter, more or less modified, or entirely 
transformed by the processes of the animal body. 

1032. Formation of blood. — The blood 
of the l *forma- * s > as ft were, the river upon which the 
Hon of the material required for animal growth is 

floated to its destination. This complex 
fluid will therefore first engage our attention. The 
food having been ground up by the teeth, and moist- 
ened by the saliva, is conveyed to the stomach and 



THE BLOOD. 413 

submitted to the action of the gastric juice. Here it is 
converted into a uniform greyish semi-fluid mass called 
chyme. The chyme is pushed forward by sponta- 
neous contraction of the stomach. It yields its nutri- 
tious matter, in the form of a milky liquid called 
chyle, to minute absorbent vessels distributed upon 
the surface of the intestines. Through these absorb- 
ent vessels it passes into the general circulation and 
is converted into blood. 

What are the 1033. TRANSFORMATION OF THE FOOD. 

offices of the The transformation of the nutritious por- 

gastncand . r 

pancreatic tion of the chyme into chyle, is effected 

juices? in p ar( . b y the gastr j c j ll i cej ail d J n part by 

the secretion of the pancreas. The latter organ lies 
back of the right end of the stomach, and pours its 
secretions into the duodenum, or first of the small in- 
testines. The gastric juice dissolves the protein com- 
pounds of the food, while the secretion of the pan- 
creas transforms the sugar and starch of the food into 
grape sugar. The chyle is thus perfected and pre- 
pared to be drawn off from the refuse portions of the 
food. As sugar forms no part of healthy blood, we 
must suppose that it undergoes immediate transforma- 
tion into fat or other material as soon as it enters the 
circulation. The office of the bile which is secreted 
by the liver and poured into the intestines, is not tho- 
roughly understood. 

1034. The gastric juice. — The saliva 

To what is the .... , n . , , ~ ^ . 

solvent agency which is mingled with the food m masti- 

of the gastric cation has an effert s i m il ar t0 that of the 
juice due f ' 

secretion of the pancreas. Another of its 



414 ANIMAL CHEMIeJTBY. 

probable agencies is to introduce air into the stomach, to 
act upon its lining membrane and produce from it one 
of the constituents of the gastric juice. The solvent 
agency of this fluid is in part owing to the ferment 
thus formed, and in part to the free acids which it con- 
tains in solution. The latter are phosphoric, hydro- 
chloric, butyric and lactic acids, in part free, and partly 
in the form of salts. 

1035. Composition of the blood. — 

(Jive the com- _ 

position of the If fresh blood is beaten with a branched 
stick, it is separated into a slightly alka- 
line liquid called the se? % um, a fibrous material called 
fibrine, and red globules, which sink, after a time, to 
the bottom of the vessel. The fibrine adheres in threads 
to the stick with which the operation is performed. It 
is analogous in composition and properties, to the vege- 
table gluten from which it is formed. The serum con- 
tains albumen, and resembles the white of egg. The 
globules are also principally albumen, with a small 
proportion of a red coloring matter called hematosine. 
Albumen and fibrine both contain phosphate of lime or 
bone earth. The serum contains, also, certain salts, 
and a small proportion of fat. All of these substances 
together form but about one-fifth of the blood ; the 
remaining four-fifths are water. When blood is left to 
stand, after being drawn from the body, the fibrine coag- 
ulates spontaneously, entangling and taking with it the 
red globules, and thus separating them from the serum. 

1036. Animal nutrition. — It is evident 
ahte n }ound from the preceding paragraph that much 
ready formed f the mate rial required to build up the 

in the blood ? u _% , 

body is found ready formed in the blood. 



BONES, FLESH, ETC. 415 

It has been transferred to it from the vegetable world 
without material change in composition. Thus the 
fibre which is required for muscle, and fat to fill out the 
tissues, require only to be built into their places in the 
animal frame, as a mason lays up a wall from materials 
provided to his hand. For the production of other 
animal substances, essential changes are required. The 
power of selection and appropriation of the proper ma- 
terials for every organ and every secretion, is found to 
reside in innumerable minute cells, which are distributed 
in every part of the body, and are endowed **rith pecu- 
liar powers according to the offices they are designed 
to fulfill. 



BONES, FLESH, &c. 
1037. Bones. — Bones consist of earthy 

Wliat is the . J 

composition of matter and a cartilagenous material com- 
b it n s e hLnT iS monl y known as gelatine. The bone 
earth or mineral matter is principally 
phosphate of lime, and forms in mammiferous animals 
about two-thirds of the whole weight. The remaining 
third is cartilage. Either of these constituents may 
be removed from the bone without effecting its shape. 
By removal of the cartilage, a brittle, earthy frame- 
work remains. By removal of the earthy material, a 
perfectly flexible mass is obtained, of a form entirely 
similar to that of the original bone. The first change 
may be effected by long digestion in dilute muriatic acid, 
and the latter by fire. If in the second process the car- 
tilaginous matter is not entirely consumed, bone black 



416 ANIMAL CHEMISTRY. 

or animal charcoal is produced, the uses of which 
have been already described. 

Of ichat does 1038. Flesh. — Lean flesh or anima 

flesh consist ? muscle is composed of fibrine, penetrated 
by a liquid which forms four-fifths of the whole, and is 
called flesh fluid or juice of the flesh. It contains a 
peculiar organic acid possessing the flavor of broth, 
crystalline substances called creatine and creatinine, 
and certain salts. Being extracted by cold water and 
then heated, it forms a nourishing and highly flavored 
soup. Hot water coagulates its albumen and prevents 
its escape from the flesh. Gradual heating is on this 
ground to be recommended in the preparation of soups, 
while sudden exposure to a high temperature, both in 
boiling and roasting, yield more nutritious and highly 
flavored meats. The salts of potash prevail in the flesh 
fluid, while those of soda are more abundant in the 
blood. Unlike the blood, this fluid is acid in its re- 
action. 
rri ., 1039. Skin, tendons, ligaments. — The 

What ts said 

of tendons and cartilaginous material above mentioned as 
igaments. a constituent of bones, is transformed by 
boiling water, without change of composition, into 
gelatine or glue. The skin, cellular membrane, tendons 
and ligaments of the body undergo the same change, and 
yield the same product. Gelatine may even be prepared 
from refuse leather, by first extracting the tannin, and 
thus reducing it to the condition of the original hide. 
The tannin obtained in the process may also be em- 
ployed for tanning new hides. Hoofs, hair, horn and 
feathers, although very similar substances, are not thus 
affected by boiling. 






GELATINE HIDES. 417 

What isgela- 1040. Gelatine. — Gelatine is soluble in 
ti^ ? water, and yields a stiff jelly on cooling 

from a hot solution. On this property is based its use 
in the preparation of jellies for the table. The com- 
mercial article employed for this purpose and ordinary 
glue are essentially the same. 

1041. The substance known as isin- 
position and glass, is the dried air bladder of a species 
P dati!iT ° f °f stlir g eon > an( l forms in its natural con- 
dition a soluble gelatine. Gelatine contains 

the four principal organic elements ; nitrogen and oxy- 
gen being in somewhat larger proportion than in the 
protein bodies. Hoofs, hair, and the other substances 
above mentioned, contain sulphur in addition. Gelatine 
is susceptible, like the protein bodies, of putrefaction, 
and also of exciting fermentation. As starch is changed 
into sugar by the action of dilute sulphuric acid, so by 
the action of oil of vitriol, gelatine may be converted 
into a sweet crystalline substance called glycocoll or 
sugar of gelatine. 

1042. Hides, tanning. — A solution of 

\V7iat chemical 

combination gelatin forms with tannin or tannic acid 
occurs^ in tan- a tenac i 0lls insoluble precipitate. The 
tanning of leather depends on the forma- 
tion of this insoluble compound in ,the hides which 
are submitted to the process. They are im- 
mersed for this purpose in an infusion of oak 
and hemlock bark, until the combination has 
taken place throughout the whole thickness. 
They are thus secured against putrefaction 
and converted into firm, elastic leather. Hides may 

18* 




418 ANIMAL CHEMISTRY. 

also be preserved by soaking them in alum and after- 
ward in oil. Soft chamois' leather is prepared by 
working the skin with fat alone. 



FATS. 

Trr , . ." 1043. Composition. — We have already 

What is said *•-■■'• 1 -, <* 

of the consti- seen that there are both acids and bases of 
tution of fats? purely organ i c origin, and that these may 

combine like the similar compounds of inorganic chem- 
istry, to form salts. The animal fats and oils are mix- 
tures of such compounds in different proportions. The 
principal of these organic salts are stearine, margarine, 
and oleine. Stearine is solid, oleine fluid and marga- 
rine occupies a middle position between the two. The 
difference of consistence in butter, lard, and tallow, 
is owing to varied proportions of these three substances 
which enter into their composition. Beside the fats 
contained in other parts of the body, the brain and 
nerves of animals contain, with albumen and water, 
certain peculiar acids and fats. 

1044. Separation of fats in oil. — 

How may the . . 

constituents of The stearme and oleine of whale oil sep- 

?ated? epa ' arate s P ontaneous ly in c °ld weather. The 
cold which is sufficient to harden the for- 
mer, leaves the latter in a fluid condition. This effect 
is often observed in lamps during winter weather. The 
case is quite analogous to the separation of cider into 
alcohol and water by freezing. The water congeals, 
and leaves the alcohol fluid. Both separations are im- 
perfect. As the alcohol produced by the above process 



FATS. 419 

is diluted to a large extent with water, so the oleine 
retains a considerable portion of stearine in solution. 

1045. Separation of fats in tallow 

How may the . . . 

different fats and lard. — Stearine is obtained from lard 
fepfratedF and tallow on a similar principle. It har- 
dens on partially cooling the melted fat, 
forming a mass from which the fluid oleine may be sep- 
arated by pressure. Stearine thus obtained is used in 
the manufacture of candles, while the oleine forms 
lard or tallow oil. The former has, of late years, given 
place to stearic acid, procured from the same sources 
by means to be hereafter described. Margarine may be 
separated from butter by similar heating and slow 
cooling. It is regarded by some chemists as a simple 
mixture of stearine and oleine and not a distinct sub- 
stance. 

1046. Glycerine. — Glycerine is the base 

What is gly- 

cerine? How of all the fatty salts which have been 
is it made? mentioned. It is a viscid, sweetish liquid 
containing the same elements as grape sugar, and in 
nearly the same proportion. On removing the stearic, 
and oleic acids from melted stearine or oleine, it re- 
mains in the liquid form. This removal may be ef- 
fected by lime. The white lime compound floats 
upon the water which is used in the process, while 
glycerine is dissolved. 

How is stearic 1047. Stearic acid.— The compound 
acid made? formed by lime, as described in the last 
paragraph, if tallow has been used in the process, is a 
mixture of oleate and sterate of lime. From these, 
stearic and oleic acids are liberated by the agency of 



420 ANIMAL CHEMISTRY. 

diluted oil of vitriol. The material floats on the dilute 
acid, gradually losing lime and becoming transparent 
by its action. Sulphate of lime or gypsum is formed 
at the same time and sinks to the bottom of the vessel. 
The stearic and oleic acids are drawn off while yet 
warm, and run into cubical moulds. The latter is sub- 
sequently removed from the mixture by gentle heat 
and pressure. The remaining stearic acid is then re- 
melted and allowed to cool slowly. It is thus ob- 
tained in a brilliant white mass, of crystalline texture, 
with the lustre of mother of pearl. This material is 
principally employed in the manufacture of candles. 
Its superiority to stearine for this purpose, consists in 
the fact that it is less softened by heat. The two sub- 
stances differ in their melting point about ten degrees. 
1048. Soaps. — Soaps are compounds of 

How are pot- . ♦_ . 

ash and soda stearic and oleic acids with caustic potash 

paredf re ' or soda '* The y are P roduced h Y boiling 
fats with either of the alkalies, till the 
mixture becomes nearly or quite transparent. The 
glycerine which is expelled from the fats in the process, 
remains mixed with the soap which is produced. Pot- 
ash soaps are soft. Soda soaps may be converted into 
a floating coagulum, and separated from the water used 
in their preparation by means of common salt. This 
method is employed to give them their hardness. The 
action depends on the insolubility of the soap in salt 
water. Salt added to potash soap seems to have the 

* In the ordinary preparation for soap making, the lye is made to 
pass through lime in the leach tub, that its carbonic acid may be par 
tially removed. 



MILK, BUTTER, ETC. 42) 

same effect. Bat its action in this case is due to a 
double decomposition, in which a floating soda soap is 
formed, chloride of potassium remaining in solution. 
Soaps may be also made without the use of water, by 
combining oil or fat with melted potash. 

1049. Liniments, &c. — Soaps are soluble 

Jioic are trans- . . L 

parent soaps in alcohol, forming the tincture of soap 

PJSS?" 11 which is used for bruises. With the ad- 
dition of camphor, this tincture forms opo- 
deldoc. Transparency is imparted to soap by the evap- 
oration of an alcoholic solution of the well dried mate- 
rial. Liniments are soaps prepared from ammonia and 
oil by the simple agitation of the materials. 
„ _ . , 1050. Properties of soaps. — Soaps 

Explain the J 

cleansing ac- which are prepared, as above seen, from 

Hon of soap. ^ an( j ^ haye the property of dissol . 

ving more of the same material. On this property 
their cleansing effect principally depends. When they 
are dissolved, a portion of the alkali becomes free by 
the substitution of water as base. This free alkali 
adds to the cleansing effect, by its own affinity for the 
oils and other organic matter. Alkalies alone axe not 
equally effectual ; they tend to shrink the fibre of cloth, 
and thus protect it against a perfect purification. The 
strength of the tissue is at the same time gradually im- 
paired. 

MILK, BUTTER, &c. 

,- . 1051. Milk. — Milk is analogous to 

What is the . . . ° . 

composition of blood in compositon, as is implied in the 
milk? office which it fulfills in the nutriment of 



4:22 ANIMAL CHEMISTRY. 

the young animal. But casein takes the place of the 
fibrin of the blood, and fat is also found in milk in 
much larger proportion. This fluid also contains sugar 
which is peculiar in its character and has therefore 
received the name of sugar of milk. Butter is pro- 
duced by the coalescence of the small particles of oil 
which are suspended in milk, and partially separated in 
the cream. Chemically considered, it is a mixture of 
oleine and margarine. On partially cooling melted 
butter, the latter collects at the bottom of the liquid 
oleine, which forms the other constituent ; a portion 
at the same time remains in solution. Beside the 
above substance, butter contains phosphates and other 
salts, with certain neutral fats from which it derives 
its flavor. 

1052. Cheese. — On exposure to the air 

WJiy is the . , . . , 

curd separated for a considerable time, the sugar contained 
by exposure? ^ n m nk [ s partially converted in lactic acid, 
and the casein is precipitated. One reason of this pre- 
cipitation is to be found in the neutralization of the 
free alkali of the milk. The casein having thus lost 
its solvent assumes the solid form. The coagulation 
of milk may also be effected by rennet, which con- 
sists of an infusion of the lining membrane of the 
stomach of the calf. Its mode of action is not well 
understood. 

1053. Solid milk. — -Milk may be 
milk'prT- 10 brought into the solid form by careful 
pared? evaporation with a moderate heat. It 

must be constantly stirred during the process. A ma- 
chine has been recently patented which secures all of 



CHEMICAL CHANGES. 423 

these objects. With the addition of a little soda and 
gum, milk may be thus kept sweet in the solid condition 
for many months. The addition of water is all that 
is necessary to reproduce it in its original form. 

CHEMICAL CHANGES IN THE ANIMAL BODY. 
..,. , 1054. Certain important changes which 

What is said r ° 

of changes in are constantly occurring in the animal body 
b h odyt mal ^main to be considered. The body is 
not the same in any two successive mo- 
ments of its existence. Every breath exhales a por- 
tion of its substance into the atmosphere, and every 
effort, whether of brain or muscle, is accompanied by 
some transformation in the .material of which it is 
composed. 

1055. Changes in the blood. — By com- 

^Aientton cer- 

tain changes paring the blood of animals with their 
in the blood? food? it win be evident that certain mate- 
rials have been not only modified, but entirely trans- 
formed in its production. Starch and sugar ^ire impor- 
tant constituents of the food, but they form no part of 
healthy blood. They are transformed into fat or other 
material as soon as they enter the circulation, and in 
this new form constitute the fuel from which the heat 
of the animal body is derived. Other changes which 
occur in the blood will be mentioned in subsequent 
paragraphs. 

1056. Animal heat. — The oxygen 

~\Vh(it is the • 

source of an- which is necessary for the slow combustion 
imaiheat? of the mater i a i above mentioned, is taken 
into the blood in the course of its passage through 



424 ANIMAL CHEMISTRY. 

the lungs. It passes on with them, through the ar- 
teries, into the minute capillary vessels which are 
distributed throughout the body. In these vessels 
their combination takes place, with the same produc- 
tion of carbonic acid and evolution of heat, as if 
the material were burned in air or oxygen gas. The 
carbonic acid thus formed is carried back to the lungs 
in the venous blood, and there exhaled, through the 
thin membrane of the air cells, and exchanged for a 
new supply of oxygen gas. In view of the relations 
of starch and sugar to the process of respiration, as 
above shown, they have been termed the respiratory 
constituents of the food. 

1057. Respiration. — In cold weather 

What is said . . 

further of res- a larger amount of oxygen is inhaled with 
pirahon . every breath, in consequence of the greater 

density of the air. Respiration is also involuntarily 
hastened, and the blood, from the two causes combined, 
becomes more thoroughly impregnated with oxygen 
gas. The transformation or combustion of the respi- 
ratory constituents of the blood, proceeds more rap- 
idly in consequence, and more internal heat is pro- 
duced to oppose the external cold. This is one of the 
provisions of nature by which the animal body is ena- 
bled to resist the influence of the seasons and of cli- 
mate. Labor has the same effect as cold in hastening 
respiration and necessitating a larger supply of food. 

What change 1058 ' CHANGE IN COLOR OF THE BLOOD. 

of color does p r0 m the fact that the globules of the 

the blood ex~ . 

perience in the blood undergo a change of color in the 
lungs? lungs, where oxygen is absorbed, it is pre- 

sumed that they serve, by absorption of the gas, as the 



FOOD AND TEMPERATURE. 425 

medium for its conveyance through the body. As 
a consequence of the changed color of the globules, 
arterial blood is of a bright scarlet, while venous 
blood is dark red. The same change of color which 
takes place in the lungs, may be readily produced by 
agitating blood drawn from the veins with air or ox- 
ygen gas. 

What is said 1059 - Relations of food and tem- 

of the reia- perature. — In proportion as the draft of 
and tempera- a furnace is increased, more fuel must be 
ture ' supplied for its combustion. For the same 

reason more respiratory food must be taken into the 
system, in proportion as more atmospheric oxygen is 
inhaled. The fact that a larger quantity is required in 
northern climates thus receives a scientific explanation. 
The preference entertained in arctic regions for cer- 
tain kinds of food, is also accounted for by the same 
necessity for increased resistance to the external cold. 
The train oil and fat which the Greenlander con- 
sumes with avidity, are a better fuel in the animal 
body than the starch which form a principal part of 
the food consumed in warmer climates. The chemical 
reason of this difference is found in the fact, that 
starch and allied substances contains oxygen in larger 
proportion. They are, as it were, in their natural con- 
dition, partially burned or oxidized substances. 

1060. Change of the animal tissues. 

What change 

takes place in In proportion to the muscular or nervous 

Ihlbodu 6 ?^ activity of the animal, the substance of 

the body is disorganized and returned to 

the blood from which it was produced. From the 



4:26 ANIMAL CHEMISTRY. 

blood it is finally removed by the kidneys, principally in 
the form of urea and uric acid, and thrown off as waste 
material from the system. These substances, although 
organic, may be figuratively regarded as the ashes of 
the consumed muscle and other nitrogenous constitu- 
ents of the body. A portion of the carbon and hy- 
drogen of the animal organs has at the same time dis- 
appeared, like the elements of respiratory food, in the 
form of water and carbonic acid. 

What is 1061. Urea. — Urea, when separated 

said of Urea? f r0 m its solution, is obtained as a white 
crystalline solid. Its molecule contains four atoms of 
hydrogen, to two each of carbon, nitrogen, and oxygen. 
When left in contact with the mucus with which 
it is accompanied in the secretion of the kidneys, 
it is speedily converted, by combination with four 
molecules of water, into carbonate of ammonia. Urea 
may also be artificially produced from cyanic acid and 
ammonia. This cyanate is identical with urea in 
composition, and is converted into urea by solution in 
water and evaporation. It was among the first of 
organic bodies artificially produced. Uric acid con- 
tains the same elements with a larger proportion of 
oxygen, and also yields ammonia by its decomposition. 
Besides the above substances, the secretion of the kid- 
neys contains various soluble salts, which have formed 
part of the body. The insoluble salts are removed 
from the system by other means. 

1062. Disappearance of fat. — Starva- 

What is said 1 . 11T . , r . 

of the disap- tion. — When the supply of respiratory 
pearance of f 0( j j deficient, nature avails herself of 

fat / ' 

the fat previously stored in the animal 



FOOD. 427 

body, as fuel to sustain the animal heat. It is taken 
up by the blood, and burned in the capillary vessels, 
as before described. This happens in the case of the 
bear and other hybernating animals. Lying dormant 
during the winter season, their fat is consumed, and 
they emerge lean from their dens in the spring. Where 
food is deficient and there is no accumulation of fat to 
supply its place, the muscle and other portions of the 
body are consumed, and death by starvation is the con- 
sequence. 

1063. Repair of the tissues. — As fast 

How are the 

tissues repair- as the worn out matter of the muscles 
and other organs is removed, its place is 
supplied in the healthy body by new material from the 
blood. Through it, also, the phosphates of the soil 
and the vegetable world are transferred to the skeleton 
of the animal, and in smaller proportion to other parts 
of the frame. The blood is itself renewed by the 
materials of the food. 

1064. Varieties of food. — It is implied 

Mention two . . 

classes of in the foregoing, that the two classes of 

food. substances which enter into the compo- 

sition of the food of animals, subserve very different 
purposes in the animal economy. The first class, of 
which starch and sugar are the principal, serve, by their 
gradual combustion, to sustain the animal heat. They 
are included, as above stated, under the general name 
of respiratory food. The protein bodies, on the other 
hand, all of which contain nitrogen, are appropriated 
in the formation of blood and muscle ; they make up 
the sanguineous or plastic food. In view of the fact 



428 ANIMAL CHEMISTRY. 

that the respiratory food enters also, in a changed form, 
into the composition of the blood, the former term 
can scarcely be regarded as distinctive. The latter, 
which designates the office of the protein bodies in 
furnishing material to build up the organs of the body, 
is much to be preferred. 

1065. Proportions of food. — For the 

rf^/ifl^ ZS Said 

of the import- economical sustenance of animals, it is of 
IZpoftionlf i m P°rt an ce that a proper relation of quanti- 
se two kinds ty should be maintained between these two 
varieties of food. Respiratory food alone, 
provides no material for supplying the waste of the or- 
ganized tissues. Plastic food, on the other hand, is es- 
pecially adapted to this end, but is poor fuel for sus- 
taining the heat of the body. Yet in lack of other 
material, it is diverted from its natural use, and thus 
appropriated at great economical disadvantage. 
m T 1066. Nature teaches us something on 

What does na~ . . . 

ture teach on this subject, in the composition of milk 
this subject? and those gra j ns w hich constitute the 

principal food of man. It will be found by reference 
to the table in the Appendix, that the quantity of 
respiratory matter in these substances, is from three to 
six times greater than that of the plastic material. 
When the object is to fatten an animal, the proportion 
of respiratory matter may be considerably increased 
by the use of potatoes, rice and other farinaceous food. 
Being furnished in excess, it accumulates in the body 
in the form of fat. Working animals, on the other 
hand, must be supplied with nitrogenous or plastic 



ORGANIC ANALYSIS. 429 

food in large proportion. The use of bacon with 
peas, beans, and eggs, and many other popular mix- 
tures of food,* are accounted for on the principle above 
stated. For the development of most of the views 
presented in this chapter, the world is indebted to the 
distinguished Liebig. 



ORGANIC ANALYSIS 

1067. Ultimate analysis. Carbon and 

How are car- 

bonandhy- hydrogen. — The proportions of carbon 
mined? det€r ' an( * hydrogen *** organic substances, is 
ascertained from the quantity of carbonic 
acid and water which they yield on combustion. The 
combustion is effected in a glass tube, by means of 
oxide of copper, and the products are collected by 
means similar to those described in the process for an- 
alyzing the air. 

1068. Nitrogen and oxygen. — The pro- 

How are nitro- . . . 

gen and oxy- portion of nitrogen in an organic substance 
ge^ndeter?mn- i s llsua iiy determined by the quantity of 
ammonia it will yield by combination 
with hydrogen. This combination is effected by 
heating the organic substance with hydrate of potassa 
or soda. The quantity of the ammonia produced in 
the process is estimated by the amount of acid it will 
neutralize. From the weight of this compound, that 
of the nitrogen it contains is readily calculated. The 
amount of oxygen in an organic substance is ascer- 
tained by subtracting the total weight of all the other 
constituents. 



430 ANIMAL CHEMISTRY. 

How are or- 1069. PROXIMATE ANALYSIS. Wb$M it 

ganic bodies [ s desired to separate organic bodies from 
from each each other, and determine *their relative 
other? proportion without reference to their ele- 

mentary composition, the methods are analogous to 
those of inorganic chemistry. Distillation, and the 
analysis of the fats, which have been already described, 
may be taken as examples. 



CHAPTER IY. 



CIKCULATI01S" OF MATTER. 

1070. The relations of the three king- 

What proves ° 

the relation doms of nature have been already inciden- 
°L%ms e of tal1 ^ considered in former parts of this 
nature? work. It remains to present the subject 

in a single view. It is obvious, at a glance, that the soil 
does not furnish all the material which is required for the 
wants of vegetable life. The level of our meadows 
is not lowered by removal of successive crops, nor 
does the forest dig its own grave at its roots as it lifts 
its ponderous trunks into the air. The atmosphere, 
as well as the soil, contributes to the increase of mass, 
whether of wood or grain, and indirectly feeds all 
races of animal existence. The relation of the three 
kingdoms of nature is thus established. 

1071. Water is one of the principal 

How does wa- , 

ter serve in agents in the system of circulation of 
^circulation matter which constitutes the life of the 

of matter f 1 

globe we inhabit. In the fulfillment of its 
office, it passes incessantly from sky to earth, now 
mingling with the currents of the atmosphere, and 
anon with those which form the arteries and veins 
of the great world of waters. Lifted into the atmos- 

19 



4:32 ANIMAL CHEMISTRY. 

phere by the sun, it descends again in dew and rain, 
corroding and dissolving the rocks on which it falls, 
and distributing them widely over land and sea. 

1072. It settles through the stony crust 

What distinct _ . 

office does it oi the earth, into the dark recesses of the 
^ u ^ ' rocks where crystals blossom out of the 

formless stone, and supplies them with the material 
for their wonderful architecture. It penetrates the 
soil, and supplies the same material to the roots of 
plants for the still more wonderful creations of leaf, 
and fruit, and flower. Again it hastens through 
brooks and rivers on its course, and pours its burden 
into the sea, for the use of the innumerable forms of 
vegetable and animal life which inhabit its waters. 
The coral insect builds up solid islands out of the mat- 
ter it provides. Countless shell-fish clothe themselves 
in the same rocky garments, and finally cast them aside, 
to be buried under the slime of the sea and harden, in 
the course of ages, into stone. The water which has 
served these various offices, climbs anew into the 
heavens upon the solar rays, and again descends in 
the rain, repeating forever its round of service to the 
earth. 

1073. The further relations of the three 
furtCrlel" kingdoms of nature may be presented in 
threl °Un he - a single picture. Imagine a giant tree, the 
doms be illus- representative of all the vegetation of the 

earth, spreading wide its branches as a shel- 
ter for man and beast. Let us suppose them to subsist 
entirely upon its fruit, and to warm themselves by fires 
made from its branches. The tree, through its leaves, 



CIRCULATION OF MATTER. 433 

draws its supply of gaseous food from the atmosphere, 
and through its roots, its mineral sustenance from the 
soil. It has purified the air in the process, of gases 
which would become noxious by accumulation, and 
returned to it the oxygen which is the vitalizing breath 
of the animal world. The mingled material of its 
food, worse than worthless to animals, has, at the same 
time, been transformed into wood and fruit, and other 
forms of vegetable matter. " 

1074. At this point, without interruption 

Explain the .... ~ 

return of mat- m the circuit, commences the return 01 
ter to the at- ma t e rial to the atmosphere from which it 

mo sphere, r 

was derived. Animals that feed upon the 
fruit of the tree, already breathe much of it back 
again to the air while they live, and the rest is re- 
stored by their death and subsequent decay. Leaves 
that fall and moulder, and branches that are burned as 
fuel, make the same return of the elements of which 
they are composed, to the great reservoirs of the at- 
mosphere and earth. And what happens thus to leaf 
and fruit, happens also at last to the parent tree itself. 
One by one its giant branches fall and moulder, and 
melting again into the air, add to its inexhaustible 
stores of fertility, and provide the material for a new 
round in the grand system of circulation. 

1075.— What happens beneath the single 

Illustrate the 

extent of these tree, occurs also in every flower that lilts 

relations. ^ peta j s to fa Q gun? an( J j s a thousand 

times repeated in every forest upon the face of the earth. 
No limits of distance or of size restrict the mutual rela- 
tions and dependencies of nature. The exhaled carbon 

19 



434 ORGANIC CHEMISTRY. 

of the polar bear feeds the lotus of Egyptian plains, 
and the breath of the southern lion is redistilled in the 
fragrance of the Norwegian pine. The particle of mat- 
ter that once burned in the firo of the poet's brain and 
floated with his song upon the air, now blooms in the 
mountain flower and anon lies buried in its mould. 
m . 1076. According to the view thus pre- 

material sour- sented, it will be seen that the sun is the 
If the l tlrlt? § reat material source of the life of the world. 
He wings the vapors that rise from the sea, 
and fall again to make their ministering circuit in 
the earth. The solar rays are the agents also, in the 
transformation of matter, which takes place in every 
leaf and blossom, and provides the animal kingdom with 
its food. 

1077. No less is the sun the source of 

Show how it is . . 

the source of all the mechanical power which is known 

mechanical upQn the earth< The faUing floo( j of m _ 

agara is but the recoil of the spring which 
is bent in evaporation from the sea and earth. All 
force which is derived from the fall of water, is 
thus traceable to the sun, which lifted it in the form of 
cloud and vapor. The energies of fire and steam, are 
only other forms of the force inherent in the solar rays, 
originally exercised in the organization of the vegetable 
matter which serves as fuel. Immediately produced 
by oxidation and the heat which it evolves, they find 
their ultimate source, as well as their precise equivalent, 
in the deoxidizing influence of the solar rays. The 
forces of the human body are fed by consumption of 
similar materials, and may therefore be traced to the 
same source. 



CIKCULATION OF MATTER. 



435 



1078. Every planet that surrounds with 
influence Km its orbit the great centre of our system, is 
the sun? equally dependent upon his influence. 

Held in their courses by his attraction, and encircling 
him in ceaseless revolution, they draw from the parent 
orb the strength and beauty which clothes their 
lesser spheres. What wonder, that in vague acknowl- 
edgement of his influence, heathen have acknowledged 
the sun as their God, and worshipped at his shrine. 
How natural that Christian nations should find in his 
life-giving power, a fitting emblem of the gloiy and 
beneficence of the great Father of the Universe, by 
whom all suns and systems, are, and were created. 





jar;** 




APPENDII. 



In this Appendix are included formulas descriptive of chem 
ical reactions, and other matter no less important, whose in- 
troduction into the text would have interfered in a measure 
with the plan of the work. 

The formulae constitute a precise statement, in the lan- 
guage of the symbolical nomenclature, of the reactions al- 
ready described in more general terms. It is not to be 
understood from the formulae that the materials concerned 
in any process must always be brought together in the pre- 
cise proportions indicated in the first member of the equation. 
One or the other may be in excess ; if so, the excess is null, and 
not considered in the formula. The latter regards and indi- 
cates only the relative quantities which are actually concerned 
in each reaction — the first member having reference to the 
materials employed, and the latter to the products. 

Interpreted according to the atomic theory, each formula 
gives on the one side of the equation, the nature and rela- 
tive number of the atoms or molecules which take part in 
any reaction, and on the other, the nature and relative num- 
ber of those which result. 

The student will do well, as an occasional exercise, to cal- 
culate from the formulae the relative quantities of materi- 
als required in a reaction, and of products resulting from it 
in pounds and ounces. A T in the tables stand respectively 
for acetic and tartaric acids. 



43S 



APPENDIX. 



§160. 

The numbers given in the text are only approximations. 
The exact quantities may be readily calculated by the law 
of expansion and contraction of gases and vapors previously 
given, taking the volume of steam at 212° (§ 193,) as a start- 
ing point. 

§ 232. 

According to the most recent determination, by Regnault, 
the latent heat of steam is 966 # 6°. According to the same 
experimenter the sum of the latent and sensible heat is not 
rigorously constant. 

§ 235. 

The apparatus commonly employed in the laboratory for 

distillation, consists of 



a retort and receiver, 
as represented in the 
figure. In Liebig's ap- 
paratus, for the same 
purpose, the vapors are 
made to pass from the 
retort or flask through 
a long inclined tube. The latter is enclosed in a second tube, 
which is constantly supplied with cold water. A more per- 
fect condensation is thus effected. 




§248. 

Active force of the galvanic current. — The active 
force of the galvanic current, is directly as the ichole electro- 
motive force in operation, and inversely as the sum of all the 



APPENDIX. 



439 



impediments to conduction. The above is Ohm's law. By 
the electro-motive force, is to be understood the whole force 
generated by the chemical action in the battery. The im- 
pediments are found in the imperfect conducting power of 
the bodies, whether liquid or solid, which enter into the cir- 
cuit, and the resistance which the current encounters in 
passing from one to another. 

§ 273. 

Smee's Battery. — Of all the batteries in common use, 
Smee's, which is represented in the figure, 
is the simplest. It consists of a plate of 
silver, with plates of zinc hanging near it 
on either side. The two zinc plates com- 
municate with each other by a metallic 
connection, and are, therefore, but one 
plate. It is found best to roughen the 
silver with platinum black. Smees' bat-I 
teries are commonly sold in this condition. 
The clamp and bar are simply to keep the 
plates in place. Water acidulated with 
from one-seventh to one-sixteenth of its bulk of oil of vitriol, 
is employed in this battery. It is generally used in plating. 

In explaining the action of sulphuric acid in this battery, it 
is best to regard it as composed of the radical S0 4 and Hy- 
drogen (p. 449). Substituting S0 4 H for CI H, the explan- 
ation given in paragraph 271 of the text applies to this case 
also. 

Groves* Battkry. — In Groves' battery the metal plati- 
num is used instead of copper or silver. It is placed by 
itself in a porous earthern cup containing nitric acid. The 
vessel is placed in a larger one containing zinc and sulphuric 
acid. The two acids mix to some extent through the pores 
of the inner cup, so as to complete the circuit by their con- 




440 



APPENDIX. 




tact. Without this the battery could not ope- 
rate. No hydrogen is evolved in this battery. 
Travelling along from the zinc in successive de- 
compositions (271), it comes upon N0 5 , at the 
point where the two acids meet. H 3 here combines 
with 3 of the N0 5 , and the residual N0 2 takes 
3 from the next N0 5 . This action continues till 
the platinum surface is reached where N0 2 is 
evolved changing to red fumes of hyponitric acid 

in the air. 

§307. 

The atomic theory. — That combination takes place in 
definite and multiple proportions, is directly proved by exper- 
iment. Oxygen, for example, unites with hydrogen in the 
proportion of 8, 16, 32 and 40, to one of the latter element, 
and refuses to combine in any other proportion. If matter 
were infinitely divisible, no reason can be assigned for this 
fact. Each infinitesimal portion of oxygen possessing the 
same affinities, we should expect to find combination in exact 
proportion to the quantity supplied. 

Dalton's atomic theory, the truth of which is assumed in the 
text, affords a luminous explanation of the facts under consid- 
eration. According to this theory, oxygen combines with hy- 
drogen in no smaller proportion than that of 8 to 1, because 
this is the ratio of weight in the least existent particles of the 
two substances. It combines in the proportion of 16, 24, 32 
and 40, by uniting 2, 3, 4 or 5 of its atoms to one of Hydro- 
gen. It refuses to combine in any intermediate ratio, be- 
cause its atoms are indivisible. The same view of the con- 
stitution of matter is essential to the explanation of innumer- 
able facts in organic chemistry. 

The value of a table of atomic weights does not depend in 
the least degree upon the reception of the atomic theory. 
It is a list of combining proportions, determined by careful 



APPENDIX. 441 

analysis, and reduced to a simple standard of comparison. 
Its truth is independent of all theory. 

Relations of atomic weight and density. — The com- 
parative weight of equal measures or masses of different sub- 
stances is not necessarily the same as the comparative weight 
of their atoms. The mass of iron, for example, is heavier, 
while the atom of iron is lighter than that of potassium. To 
account for the fact, we must suppose the lighter atoms of 
iron so closely arranged that they thus more than make up 
by their larger number, for their inferior weight. In solids 
generally, there is no correspondence between atomic weight 
and specific gravity ; but in the case of many elements which 
exist in the gaseous state, or are capable of assuming it, the 
correspondence is complete, as shown in the following para- 
graph. 

Combining measures or equivalent volumes. — A cubic 
foot of nitrogen, weighs just fourteen times as much as the 
same measure of hydrogen, and the relation of the atomic 
weight is the same. In combining by atomic weights or 
equivalents, they therefore combine in equal measures. 
Chlorine and the vapors of bromine and iodine belong 
to the same class. Taking hydrogen 1 as the standard, 
their combining measures are all 1. In the case of oxygen 
the correspondence referred to does not exist. It is sixteen 
times as heavy as hydrogen, while its atom weighs but eight 
times as much ; here again we are under the necessity of 
supposing a closer arrangement of the atoms. Those of 
oxygen are not only heavier, but twice as closely approxi- 
mated. Taking hydrogen as the standard, the combining 
measure of oxygen is therefore \. That of phosphorus and 
arsenic is the same, and that of sulphur \. In the case of 
most other substances the ratio is not so simple. 

In the comparison of combining measures it is more 
customary to adopt oxygen as the standard of unity. The 

19* 



442 APPENDIX. 

combining measure of hydrogen, chlorine, etc., becomes 
2, as a consequence, and that of other gases or \upors is 
proportionally changed. In the production of compound 
gases, the elements either suffer no condensation or experi- 
ence a very simple change of volume. Thus hydrochloric 
acid gas, formed by the combustion of hydrogen and chlo- 
rine, possesses the united volumes of its constituents. 

Equivalent volumes of compound gases. — As the 
equivalent or combining proportion of a compound is 
equal to the sum of the equivalents of its constituents, it 
follows that the combining measure of hydrochloric acid 
is equal to the sum of the combining measures of hydro- 
gen and chlorine, 2+2 = 4. Ammonia is formed by the 
union of three volumes of hydrogen and one of nitrogen. 
Condensation takes place to the amount of J of the whole 
volume of their mixed gases. The combining measure is 
therefore equal to the sum of the combining measures of the 
constituents divided by 2, The sum of the combining 
measures is 8. 8—2=4. Steam is composed of one com- 
bining measure (two volumes) of hydrogen, united with 
one combining measure or volume of oxygen, and condensed 
to two volumes in combination. Its combining measure is 
therefore 2. The above instances may serve as examples 
of the interesting relations of atomic weights, specific quan- 
tity and combining measures. 

Calculation op specific gravity. — The density or spe- 
cific gravity of a compound vapor or gas of known propor- 
tional composition, may be readily calculated from that of 
its constituents, supposing the amount of condensation which 
takes place in their combination to be known. The results 
thus obtained are more accurate than any results of experi- 
ment. In like manner the proportional composition of a 
compound may be calculated from a knowledge of its ele- 
ments pi?<1 density. The density of the vapor of carbon and 



APPENDIX. 443 

Dther solids which are not known in the gaseous form, may 
be calculated from the density of their compounds with ele- 
mentary gases of known density. That of carbon, for ex- 
ample, may be deduced from that of carbonic acid. The 
calculation involves an assumption as to the equivalent vol- 
ume of carbon. Assuming it to be the same as that of hy- 
drogen, the density of carbon vapor is 423 4. If its equiva- 
lent volume is the same as that of oxygen or ^ that of hydro- 
gen, the density is doubled. 

Atomic volumes. — It is obvious that the number of atoms 
of a given weight in any mass, must be in proportion to the 
density of the mass. The size of the same atoms must be 
less in the same proportion. The atomic volume of any 
substance is therefore obtained by dividing the atomic 
weight by the density or specific gravity of the body. The 
subject of atomic volumes has important relations to the 
science of crystallography. In comparing atomic volumes 
it is assumed that the space which a body occupies is com- 
pletely filled by the atoms, without intervening space. 

Atomic heat. — The numbers 28, 32, 103, represent, in 
the order in which they are given, the atomic weights of 
iron, copper ; and lead. It is a remarkable fact that if the 
three metals be taken in these relative proportions, it will 
require the same expenditure of heat to make them equally 
hot. 103 pounds pounds of lead can be heated up to 212,° 
for example, by burning the same amount of alcohol which 
will heat 32 pounds of copper, or 28 lbs. of iron, to the same 
degree. Most other metals, and the non-metallic element 
sulphur, come into the same class, or in other words, 
have the same atomic heat. The atomic heat of arse- 
nic and silver is double that of the elements above men- 
tioned. Other elements are different in this respect, but 
commonly by some simple ratio of difference. The cor- 
respondence is never absolute, but so close as to hare lead 



444 AXPENDIX. 

many chemists to attribute the variations to errors of exper- 
iment, and to regard the law of correspondence of atomic 
heat as universal. 

§313. 

Calculation of formulae. — The student interested in 
the subject will readily devise for himself the reverse pro- 
cess of calculating formulae from the per centage results of 
analysis. The formulae obtained must obviously be such, 
that if reconverted into per cents, the numbers obtained will 
agree very nearly with the results of analysis. There may 
sometimes be a doubt whether the simplest formula which 
will express the composition, or some multiple of it is the 
true one. This can only be decided by the analysis of one 
of the compounds of the substance in which the formula of 
the second constituent is established. 

The reasoning will be best illustrated by an example. It 
being assumed that neutral salts contain one equivalent of 
base to one of acid, the analysis of the neutral sulphate of 
potassa would establish the formula for sulphuric acid, S03, 
instead of S2O8. KO,S03 would express correctly the com- 
position of the salt, while the substitution of S2O6 for S 03 
in the same formula, would give a double proportion of acid. 

§ 323. 

When the same element unites with oxygen in different 
proportions to form different acids, these are distinguished 
by prefixes and terminations which indicate the order in 
which they stand to each other with respect to the quantity 
of oxygen. 

The first acid of such a series discovered, generally receives 
the termination " ic." Chloric acid may serve as an exam- 
pie. Another acid compound of chlorine since discovered, 



APPENDIX. 445 

and containing more oxygen, is called hyperchloric, signify- 
ing higher than chloric. The other names of the list indi- 
cate, by their prefixes and terminations, the order of oxy- 
genation of the several acids. The same means of distinc- 
tion are employed in other series. 

Hypochlorous acid, - CIO. 

Chlorous acid, ----- CIO2. 

Hypochloric acid, (peroxide of chlorine,) CIO4. 

Chloric acid, ... - - ClOs. 

Hyperchloric acid, .... C107. 



§332. KO,C10 5 =KCl+60. 

§334. 3Fe + 40=Fe 3 04. 

§338. P+50-P0 5 . 

§340. C+20=C0 2 . 

§354. 2HCl+Mn0 2 =2HO+MnCl+Cl. 

§ 355. (CaCl +CaO, CIO) +230 3 =2(CaO, SO 3) +2C1. 

§358. Sb+5Cl=SbCl 5 . 

§ 362. 

It will be observed, on comparing § 362 with those which 
precede, that chlorine sometimes expels oxygen, and is 
sometimes expelled by it. In relation to the apparent in- 
consistency of these facts, little more can be said than that 
chemical affinities are modified by circumstances, the action 
o'" which is not perfectly understood. 

§365. HO+Cl=HCl+0. 

§ 375. NaI+2S03+Mn0 2 =NaO,S03+MnO,S0 3 +I 

§384. S+20=SOs. 

§400. Zn+HO,S03=ZnO, SO3+H. 

§408. Cu+2S03=CuO,S03+SO*. 



446 



APPENDIX. 



§ 411. 

Iodide of nitrogen. — Iodide of Nitrogen, a very explo- 
sive compound, is formed when an alcoholic solution of iodine 
is added to aqua ammonice. It precipitates in the form of a 
black powder. The precipitate should be thrown upon a 
filter, washed, and while still moist, divided into small por- 
tions for the purpose of experiment. When dry it explodes 
violently by simple touch, and sometimes even spontaneously. 

Chloride of nitrogen. — Chloride of nitrogen is a still 
more dangerous compound than the above. To prepare it 
ajar filled with chlorine gas is suspended over a solution of 
sal ammoniac, contained in a leaden saucer. After the lapse 
of a few hours, an oily liquid forms and falls to the bottom 
of the solution. This is the chloride of nitrogen. Mere 
contact with a combustible material, such as fat, oil, phos- 
phorus, &c, is sufficient to cause its explosion. A single 
drop of the liquid explodes so violently as to shatter to pieces 
any earthen or glass vessel upon which the explosion takes 
place. The preparation of this compound cannot be recom- 
mended ; in the hands of the ablest experimenters it has 
been the occasion of the most dangerous accidents. 

§413. P+50=POs. 

§ 424. KO, N0 5 +HO, S0 3 =KO, SCh+HO, N0 5 . 

§425. 3Cu+4N0 5 =3(CuO,N0 5 )+N02. 

§426. NO2+2O-NQ4. 

§428. 3Sn+2NOi=3Sn02.+2NOa. 

§430. 3P+5N0 5 =3P0 5 +5N0 2 . 

§433. 5C+P0 5 -5CO+P. 

§446. AsCl 3 +6Zn + 6(HO, S0 3 ) = 6(ZnO, SOs + 

3HCl+AsH 3 . 
§464. C+20=:C02. 
§465. HCl+CaO,C0 2 =HO+CaCI+C02. 



APPENDIX. 447 

§478. C0 2 +C=2CO. 

§480. C 2 03,HO+S03=HOS03+C0 2 +CO. 

§490. Zn+S03+H02 = ZnO, S0 3 +H. 

§492. 3Fe+4HO=Fe 3 04+4H. 

§496. H+0=HO. 

§501. Na+HO=NaO+H. 

§519. H+C1=HC1. 

§521. HO,S03+NaCl=NaO. SO3+HCI. 

§530. Si03+3HF=3HO+SiF 3 . 

§537. N+3H=NHs. 

§ 539. CaO+NH4Cl=HO+Ca Cl+NEU. 

§543. NH S + HC1=NH4C1. 

§546. KO+3HO+2P=KO,P0 3 +PH 3 . 

§ 553. 2S03+C4Ho02=2(HO, S0 3 )+C4H4. 

§577. 2C+KO,COa=3CO+K. 

§585. Na+NH4Cl+Hg=NaCl+NH4,Hg. 

§626. Sb+5Cl=SbCl». 



§640 5 Litharge=Pb °- 
v {Red Lead=Pb 3 04 



§ 680. 
The other elements not mentioned in the text are glucinum 
cadmium, cerium, columbium or tantalum, didymium, erbi 
um, iridium, lanthanum, molybdenum, niobium, norium 
osmium, palladium, pelopium, rhodinm, ruthenium, seleni 
um, tellurium, terbium, thorium, titanium, tungsten or wol 
framium, vanadium, ytrium and zirconium. With the ex 
ception of selenium and tellurium, which are analogous in 
their properties to sulphur, they may be classed with the 
metals. They are of rare occurrence, and may be regarded 
as sustaining the same relation to the other elements as do 
die asteroids and satellites to the more important members 
of the solar system. 

§646. Zn+PbO, A=ZnO, A+Pb. 

§665. NaCl + AgO, NO*^NaO, NO«+AgCL 



443 



APPENDIX. 



§685. 



Neutral, acid, and basic salts. — In general, salts con- 
taining an equivalent of base to an equivalent of acid are 
called neutral. The composition fixes the name, whether ex- 
actly neutral to the taste and in their action or vegetable 
colors, or not. Salts containing more acid in proportion 
are called super-saks or acid salts, and those containing 
more base, sub-salts or basic salts. 

There are two exceptions to the above rules. The first 
is that of certain classes of acids which have double and 
treble neutralizing power, and require, therefore, the first two 
atoms, and the latter three atoms of base, to make them 
neutral salts. Such acids are bibasic and tribasic, in contra- 
distinction from the mono-basic or ordinary acids. Phospho- 
ric acid is one of the latter class of tribasic acids, and the 
neutral phosphates have therefore three atoms of base and 
is called a tribasic phosphate. Phosphates containing more 
acid or base than their proportion, are acid or basic accord- 

The second exception is that of salts or bases which con- 
tain more than one atom of oxygen to an atom of metal. 
In proportion as they contain more, they neutralize more acid. 
Alumina or oxide of aluminium, for example, contains three 
atoms of oxygen. Its neutral sulphate, therefore, is a salt 
containining 3 atoms of acid. A salt of aluminium containing 
more or less than their proportion, is acid or basic accord- 
ingly- 

Double salts. — There are also double salts or compounds 
of salts with each other. They are generally of the same 
acid. Thus alum is a double sulphate of potassa and alu- 
mina and the bisulphate of potassa may be regared as a 
double sulphate of potassa and water. Such double salts 



APPENDIX. 419 

are not mere mixtures. They have their own crystalline 
form, and each molecule of their crystals contains all the ele- 
ments of both salts. 

Binary theory of salts. — Sulphate of potassa, and 
other similar salts, are commonly regarded as ternary com- 
pounds. But many chemists are of the opinion that they 
are constituted after the plan of the binary salts, and their 
acids on the plan of a hydrogen acid. They would write 
sulphuric acid, S04,H, instead of HO,S03, thus indicating 
that the hydrated acid is composed of the radical, S04, (a 
compound playing the part of an element,) with hydrogen. 
Sulphate of potassa would, according to this view, be writ- 
ten K,SO<i, instead of KO,S03. The acid and salt are thus 
represented as analogous in constitution to a hydracid and 
a binary salt; thus, (S04)H corresponds with C1H, and 
K(S04) with KOI. The advantage of this view is that it 
makes but one great class of acids and one of salts, associ- 
ating substances which are analogous in their properties. 
Hydrogen thus becomes characteristic of an acid. This view 
also simplifies the subject of the production of salts from 
acids, making it to consist simply in the replacement of the 
hydrogen of the acid by a metal. Thus in the action of sul- 
phuric acid (HO,S03) on zinc, sulphate of zinc (ZnO,S03) is 
formed by the simple replacement of the hydrogen of the 
acid by the metal zinc. As will be seen more clearly in 
the introduction to Organic Chemistry, it is no conclusive 
objection against the view, that the radical SO4 has not been 
isolated. There is the best reason for believing in the exist- 
ence of many such hypothetical radicals. A similar objection 
has indeed been urged against the ordinary view, according 
to which SO3 neutralizes potassa in the sulphate of this base. 
The objection lies in the fact that anhydrous sulphuric acid 
is not possessed of acid properties, and can therefore be 
scarcely regarded as an acid, in its anhydrous condition. 



450 



APPENDIX. 



§717. CaO, HO+KO, C0 2 =CaO, CO.+KOHO. 

§725. NH 3 +HO ) S03=NH40 ) S0 3 . 

§726. CaO, C0 2 =C0 2 +CaO. 

§ 727. CaO+HO=CaO, HO. 

§741. HCl+NaO=HO+NaCl. 

§742. NaCl+AgO, NOs-NaO, NO.+AgCL 

§748. (CaCl+CaO,C10)+2CO»=2(CaO, C0 2 )+2Cl. 

§750. 2CaO+2Cl=(CaCl+CaO, CIO). 

§751. 3C+3C1+A1 2 3 =3C0+A1 2 C1 3 . 

§760. HO, S03+CaF=CaO,S03+HF. 

§762. PbO, A+HS=HO, A+PbS. 
§769. NaO+S0 3 =NaO, S0 3 . Vide §400. 
§770. (CaO, SOs+2HO)=2HO+CaO, SOs. 
§772. 2HO+CaO, S0 8 = (CaO,S03+2HO). 
§774. HO, S03+NaCl=HCl+NaO, SOs. 
§775. Glauber's Salt=(NaO, SOs + loHO). 
§777. Alum=(KO, SOa+AhOs, 3SO+24HO). 
§ 778. (KO, S0 3 + Al. Os, 3SOs +24HO) =24HO + 
(KO, SOs+AlsOs, 8SO»). 

« „ 79 < Chrome Alum=(KO, SOs+CraOs, 3SOs+24HO 

5 " I Ammonia Alum=(NH40, SOs+AbOs, 3S03+24HO) 
[Sulphate of Zinc=(ZnO, SO3+7HO). 

§780.-1 Sulphate of Copper=(CuO, SO3+5HO). 
[Sulphate of Iron=(FeO, SO3+7HO). 

§783. Nitrate of Potash (Nitre) = KO, NOs. 

§784. CaO, NOs+KO, C0 2 =CaO, COa+KO, NOs. 

§786. NH4CyNO«=4HO+2NO. 

§787. S+KO, NOr+3C=KS + N+3CO». 

§789. Nitrate of Silver (Lunar Caustic)=AgO, NOs 

§790. Nitrate of Soda=NaO.. NOs. 

§792. KO, C0 2 +Ca0, NOs=KO, N05+CaO,C0 2 . 

§795. CaO, C0 2 +NaS=CaS+NaO, C0 2 . 

§ 797. Sesqui- carbonate of Ammonia=2NH4 0, 3COa. 



APPENDIX. 451 

§804. CaO+C0 2 =CaO, CO*. 

§ 809. (2NaO, HO, PO* + 24HO) + 3(AgO, NO* = 
2(NaO,NO s ) +HO, NO* +24HO+3AgO, POs . 
§824. Bibarate of Soda=(NaO, 2BO3 + IOHO). 
§ 828. Chromateof Lead (Chrome yellow) =PbO,CrO 3. 
§829. KO, C0 2 + 2(PbO, CrOs)=KO, Cr0 3 +C0 2 + 

2PbO, CrOs. 
§ 830. Commercial chrome green is a mixture of Prussian 
blue and chrome yellow. 

§833. 3(KO, Mn0 3 )+2S0 3 =2(KO, SOs)+MnO« + 
KO, MnaOt. 

§ 845. 4NO*+3Ag+Au=3(AgO, NO*)+NOa+Au. 
§ 846. 3NH4O + CaO, NOo + Al*Os, 3NO* = 

3(NH40, NO*)+CaO,NO«+Al 3 0». 
§ 847. CuO, NO* + AgO, NOs + HC1 = CuO, NO* + 

HO, NO*+AgCL 
§ 871. During the night a reverse process of absorption of 
oxygen and exhalation of carbonic acid takes place, to a 
small extent. 

§890. Kreosote=Ci4Hs02. 

§893. <BenZ ° le=C,2H( 



'Carbazotic Acid=Ci 2H3N3O1 4 
§894. Gun Cottan (Pyroxaline^C^HsOs, 4NO5.? 
§898. C) 2 HioOio+4HO=Ci 2 Hi40i4. 
§900. Starch=Ci2HioOio. 
§904. Ci 2 HioOio+4HO==Ci 2 Hi40i4. 
§907. Grape Sugar=Ci2Hi40i4. 
§908. Cane Sugar=Ci2HnOn. 
§913. (Ci 2 Hi 2 Oi2 + 2HO) = 2HO + 2(C4H 6 2 ) + 

4CQ 2 . 
§914. AIcohol=C4H 6 2 . 
§917. C4H4+2HO=C4H 6 2 . 



452 APPENDIX. 

§919. 

Fulminates. — This name has been given to a class of 
highly explosive salts, obtained by the action of alcohol 
upon certain nitrates. The most important are the fulmi- 
nates of mercury and silver. Fulminating mercury is pre- 
pared by dissolving 1 part of mercury in 12 parts of nitric 
acid, sp. grav. 1.36, and subsequently adding 11 parts of 80 
per cent, alcohol. Upon warming the mixture a compli- 
cated reaction takes place, dense white vapors are given off, 
and the fulminate is thrown down as a crystalline powder. 
This is to be washed with cold water and afterwards dried 
at a moderate temperature. This salt explodes violently by 
heat, friction, or percussion, and sometimes even without 
any apparent cause. It is largely employed in the manufac- 
ture of percussion caps, torpedoes, &c, &c. Fulminating 
silver detonates still more violently than the mercury salt. 
By friction with a hard body, it explodes even under water. 
It is prepared as above, using ]0 parts of nitric acid and 
20 parts of alcohol Too much caution cannot be observed 
in manipulating with these highly dangerous compounds. 
They should be prepared only in quantities of a few grains. 
Fulminate of Silver=2AgO, CysCb. 

§927. Ether=C 4 H 5 0. 

( Alcohol -CiHeOs or (C 4 H 5 0+HO). 
§928, ((C4H 5 0+HO)+S03 = HO, SO3+C4H5O. 
§929. C4H5l+Zn=ZnI+C4H5. 
§930. C4H 6 02+2S03 = 2(HO, S0 3 )+C 4 H4. 
§931. C4H60 2 +20-2HO+C 4 H40 2 . 
§932. Aldehyde=C4H402. 
§933. C 4 H402+20=C4H404. 
§935. Chloroform=CaHCl3. 
§938. Tannic Aeid^C isHsOq, 3HO=Qt, 3HO. 



APPENDIX. 



453 



§941. Cyanogen=C2N=Cy. An arbitrary symbol. 
§ 942. FeCy, 2KCy +HgCl a =FeCy 5 2KCl + Hg+2Cy. 
§943. Cyanide of Potassium=KC 2 N=ECy. 
§944. Prussian Blue = Ci 8 N 9 Fe7 = Fe4Cfy 3 . 

fFerrocyanogen=3Cy, Fe=Cfy. 
Ferrocyanide of Potassium = (3Cy } Fe+2K) = 
Cfy, 2K. 
§ 946. 2(3Cy, Fe + 2K) - K = (2(3Cy, Fe) + 3K) = 

2Cfy, 3K. 
§947. KCy+HO, S0 3 = KO, S0 3 + HCy. 

'Tartaric Acid-CsHLOi o, 2HO=T, 2HO. 
Oxalic Acid=C 2 3 , HO=0, HO. 
Citric Acid=Ci2H50ii 3 3HO=Ci, 3HO. 
Malic Acid=CsH 4 Os, 2HO=M, 2HO. 
Formic Acid = C 2 H0 3 , HO. 
.Lactic Acid^CaHsOo, HO. 



§949. 



§ 975. 

In the present state of our knowledge in respect to the 
protein bodies, we must abandon every formula designed to 
express their atomic constitution. They contain in a hundred 
parts : 55.16 carbon, 1.05 hydrogen, 21.81 oxygen, 16.96 
nitrogen, with ^ to 1 per cent, sulphur and phosphorus in an 
unknown form. 



§ 991.- 



r Morphine=C3sH2 oNOe. 
Strychnine==C4 4H2 3N2O8 or C44H24N2O3. 

Quinine— C2 CH12NO2. 

Theine and CafFeine=Ci 9H1 0N4O4. 
§993. lndigo=Ci 6 H 5 N02. 
§994. Alizarine=C2 0H1 0O1 0. 
§995. Hematoxyline — C4 0H1 7O1 5 e 
§1002. Vide §994. 



454 



APPENDIX. 



§ 1003. (KO, S0 3 + CrsOe, 3SOs) + 3KO = 4(KO, 
S0 3 )+Cr 2 03. 

§ 1025. 

Mode of estimating the value of guano, &c. — In 

estimating the moriL^ value of guano for agricultural pur- 
poses, ammonia may be set down at 16 cents per pound, 
potash at 4 cents, and phosphoric acid at 1^ to 2 cents. As 
far as the latter exists in a soluble form, its value is doubled. 
Other substances are of so little comparative value that they 
need not be taken into the account. These valuations are 
based, not alone on their relative value as fertilizers, but on 
the cost of the different substances when obtained from other 
sources. They are somewhat arbitrary, but may serve as a 
means of approximate estimation of the value of guano and 
other fertilizers. 

As an average of the composition of thirteen samples of 
Peruvian guano, Prof. Way obtained the following results : 
ammonia, 17*41 per cent.; phosphoric acid, 11*13; potash, 
3*50. This would seem to be considerably above the or- 
dinary average. The pecuniary value of such an article, 
according to the above valuation, would be $63.00 per ton, 
of which $55.60 would lie in the ammonia. No distinc- 
tion is made in the potential and actual ammonia of guano, 
because the conversion of the former into actual ammonia 
takes place so rapidly in the soil. But the potential ammo- 
nia of most nitrogenous substances, as of clippings of hides 
and other similar refuse, is to be estimated at least 25 per 
cent, lower, in view of their comparatively slow conversion. 

In all analyses of concentrated fertilizers excepting guano, 
in which the first distinction may be neglected, the amount 
of actual and potential ammonia, of soluble and insoluble 
phosphoric acid, and of potassa, should be separately stated. 



APPENDIX. 



457 



TABLE II. 



ATDMIC WEIGHTS. * 

Hydr©gen=1.00, 



Uuminium 


Al 


13.63 


Lead 


Pb 


103.57 


\ntimony 


Sb 


129.00 


Lithium 


Li 


6.64 


Arsenic 


As 


75.00 


Magnesium 


Mg 


12,00 


Barium 


Ba 


68.59 


Manganese 


Mn 


27.57 


Bismuth 


Bi 


208.00 


Mercury 


Hg 


100.05 


Boron 


B 


11.04 


Nickel 


HI 


29.55 


Bromine 


Br 


79.97 


Nitrogen 


N 


14.00 


Calcium 


Ca 


20.00 


Oxygen 


O 


8.00 


Carbon 


C 


6.00 


Phosphorus 


P 


31.36 


Chlorine 


CI 


35.46 


Platinum 


Pt 


98.94 


Chromium 


Cr 


26.78 


Potassium 


K 


39.11 


Cobalt 


Co 


29.49 


Silicon 


Si 


14.81 


Copper 


Cu 


31.68 


Silver 


Ag 


107.97 


Fluorine 


Fl 


19.00 


Sodium 


Na 


23.00 


Gold 


Au 


196.67 


Strontium 


Sr 


43.67 


Hydrogen 


H 


1.00 


Sulphur 


S 


16.00 


Iodine 


I 


126.88 


Tin 


Sw 


58.82 


Iron 


Fo 


28.00 


Zinc 


Zn 


32.53 



* These atomic weights are calculated from the best and most pre- 
cise investigations ; some of them have not yet been established by 
recent experiment, but are calculated from others so determined. 

FREftE NIL'S. 



20 



458 



APPENDIX. 



TABLE III. 

SPECIFIC GRAVITY OF SOLIDS. 

Pure water at 60° F=1.000 



Platinum 20.98 

Gold, 19.26 

Mercury 13.60 

Lead 11.45 

Silver 10.50 

Bismuth 9.80 

Copper 8.87 

Cobalt 8.54 

Nickel 8.28 

Manganese 8.00 

Iron 7.80 



Tin 7.29 

Zinc 7.03 

Antimony . 6.70 

Sulphur . . . . .. . 1.98 

Chromuim 6.00 

Arsenic 5.80 

Iodine 4.95 

Aluminium 2.60 

Phosphorus 1.86 

Sodium 0.97 

Potassium 0.86 



TABLE IV. ♦ 

SPECIFIC GRAVITY OF LIQUIDS 

Pure water at 60° F=1.000 



Mercury 13.596 | Ammonia 0.870 

Bromine . . . 2.79 to 3.19 Turpentine 0.865 

Sulphuric Acid. . . . 1.800 Alcohol 0.800 

Nitric Acid .... 1.515 I Ether 0.720 



TABLE V. 

SPECIFIC GRAVITY OF GASES. 

Dry air at 60° F=1.000 



Chlorine 2.454 

Nitrous Oxide .... 1.525 
Carbonic Acid .... 1.525 

Fluorine 1.296 

Hydrochloric Ac. gas . . 1.261 



Oxygen . 1.109 

Carbonic Oxide . . . 0.970 

Nitrogen 0.970 

Hydrogen 0.069 

Ammoniacal gas . . . 0.589 



APPENDIX. 



459 



TABLE VI. 

LINEAR EXPANSION OF SOLIDS ON BEING HEATED FROM 32° TO 212° F. 



Zinc (cast) 


expands -^\z 


Iron expands y-g-g- 


Zinc (sheet) 


34 


Steel (tempered) " g-y-g 


Lead 


"3 5T 


Steel (untempered) " p-^y 


Silver 


ft 1 

5 24 


Platinum " ttVt 


Copper 


tt 1 

5 8 1 


Flint Glass " j-^jj 


Gold 


tt 1 

6 8 2 


Black Marble " 2X33 



TABLE VII. 

SPECIFIC HEAT. 

Water=1.000 



Alcohol 


. . 0.660 


Phosphorus . . 


. . . 0.187 


Ether 


. 0.520 


Iron 


. . 0.113 


Nitric Acid . . . 


. . 0.442 


Zinc 


. . . 0.099 


Oil of Turpentine . . 


. 0.425 


Arsenic . . . . 


. . 0.081 


Sulphuric Acid . . 
Carbon 


. . 0.333 
. 0.241 


Tin 


. . . 0.056 


Iodine 


. . 0.054 


Common Salt . . . 


. . 0.225 


Silver .... 


. . . 0.050 


Lime 


. 0.205 


Mercury . . . . 


. . 0.033 


Sulphur .... 


. . 0.202 


Platinum . . . 


. . . 0.032 


Glass 


. 0.197 


Gold 


. . 0.032 



TABLE VIII. 

MELTING POINTS OF SOLIDS. 



Cast Iron 


melts at 3479° 


Potassium melts at 154° 


Cobalt 


tt 


" 2800° 


Wax 


" 142° 


Silver 


u 


" 2283° 


Spermaceti " 


" 112° 


Gold 


t< 


" 2016° 


Phosphorus " 


" 108° 


Copper 


it 


" 1996° 


Tallow 


" 92° 


Lead 


tt 


" 612° 


Olive Oil 


36° 


Bismuth 


a 


497 o 


Ice 


" 32° 


Tin 


a 


442° 


Oil of Turpentine " 


" —14° 


Sulphur 


tt 


" 226° 


Mercury " 


" —39° 


Newton's Alloy 


tt 


" 208° 


Liquid Ammonia, " 


« —40° 


Sodium 


tt 


194° 


Ether 


" —47° 



460 



APPENDIX. 



TABLE IX. 

BOILING POINTS OF LIQUIDS. 



Mercury boils at 662° 


Nitric Acid 


boils at 248° 


Whale Oil 


' 630° 


Water 


" " 212° 


Sulphuric Acid " 


' 620° 


Alcohol 


u « tf^O 


Sulphur " 


M 600° 


Bromine 


" " 116° 


Phosphorus " 


u 551° 


Ether 


" " 96° 


Oil of Turpentine " 


» 312° 


Sulphurous Acid 


" " 14° 



TABLE X. 

COMPOSITION OF HUMAN BLOOD ACCORDING TO LeCANU. 



Water 


78.015 


Fibrin 


0.210 


Albumen 


6.509 


Blood-globules, • 


13.300 


Crystallizable fat 


0.243 


Oily fat. 


..... 0.131 


Salts of the alkilies 


0.837 


Salts of earths and ox. of iron 

Other substances • 


0.210 

0.545 






100.000 



TABLE XL 

COMPOSITION OF COw's MTLK. 



Water 


. . 873.0 


Casein, and a little albumen 


. . 48.2 


Butter 


. . 30.0 


Sugar of milk 


. . 43.9 


Phosphate of lime with a little chloride of calcium . . 
Phosphate of iron and magnesia, and a little soda . . 
Chlorides of sodium and potassium 


. . 2.3 

0.9 

. 1.1 


1000.00 



APPENDIX. 



461 



TABLE XII. 

RELATIVE PROPORTIONS OF THE SAXGUIGENOUS TO THE RESPIRATORY CONSTI- 
TUENTS IN DIFFERENT KINDS OF FOOD. 







Sang 


uigenous. 


Respiratory. 


Cow's milk contains, for 


10 


30= \ 8 * 8 fat and 

( 10.4 milk sugar 


Human milk 


tt 




10 


40 


Horse beans 


tt 




10 


22 


Peas 


tt 




10 


23 


Fat mutton 


tt 




10 


27=11.25 fat 


Fat pork 


tt 




10 


- 30=12,5 " 


Beef 


tt 




10 


17=7.08 " 


Veal 


a 




10 


1=0.41 " 


Wheat flour 


tt 




10 


46 


Oatmeal 


tt 




10 


50 


Rye flour 


tt 




10 


57 


Barley 


a 




10 


57 


Potatoes (white) 


tt 




10 


86 


Potatoes (blue) 


tt 




10 


115 


Rice 


tt 




10 


123 


Buckwheat 


tt 




10 


130 



Starch is the principal constituent of respiratory food in the sub- 
stances mentioned iu the table. When sugar and fat take its place, the 
fact is separately indicated, while their equivalent in starch is given 
in the principal column for convenience of comparison. The above 
table is taken from Liebig's Letters on Chemistry. 



TABLE XIIL 

PER CENT BY MEASURE OF ALCOHOL IN SPIRITOUS LIQUORS AT 62° F. 



Rum 




contains 


72 to 77 


per cent. 


Cognac 




tt 


50 " 54 


a 


Whiskey 




n 


59 


ft 


Geneva 




tt 


50 


tt 


Port wine 


tt 


21 to 23 


tt 


Sherry 


tt 


tt 


15 " 25 


tt 


Madeira 


tt 


tt 


18 " 22 


tt 


Malmsey 


" 


tt 


16 


tt 


Claret 


tt 


u 


9 to 15 


tt 


Burgundy 


tt 


u 


7 " 13 


ft 


Rhenish 


tt 


tt 


8 " 13 


tt 


Moselle 


a 


tt 


8 " 9 


tt 


Tokay 


tt 


tt 


9 


tt 


Champagne 


tt 


M 


5 to 15 


tt 



462 



APPENDIX. 



TABLE XIY. 

SOLUBILITY OF SUBSTANCES 





KO 


[NaO 


NH40 


BaO 


SrC 


>CaO 


MgO 


AI2O3 


MnO 


>FeO 


NiO 










1 


1 


12 


2 


2 


2 


2 


2 


s 








1 


1 


12 


2 




2 


2 




CI 








1 


1 


1 


1 


1 


1 


1 


1 


I 








1 


1 


1 


1 




1 


1 




S03 








3* 


3 


1 2 


1 


1 


1 


1 


1 


NOs 








1 


1 


1 


1 


1 


1 


1 


1 


POo 








2 


2 


2 


2 




2 


2 


2 


C02 








2 


2 


2 


2 




2 


2 


2 


C203 








2 


2 


2 


2 


2 


2 


1 2 




B03 








2 


2 


2 


2 


2 


2 


2 


2 


A 








1 


1 


1 


1 


1 


1 


1 


1 


T 








2 


2 


2 


i2 


1 


i2 


i2 




AsOs 








2 


2 


2 


2 


2 


2 


2 


2 


AsOa 








2 


2 


2 








2 


2 


CrCb 


V 






2 


2 


2 


1 


2 


1 




2 



EXPLANATION OF THE TABLE. 
To ascertain the solubility or insolubility of a salt from 
the above table, its acid is sought in the left hand column, 
and its base in the upper line. The square, which is in line 



APPENDIX. 



463 



TABLE XIY.— (Continued.) 

IN WATER AXD ACIDS. 





ZnO 


PbO 


SnO 


SnO 


BiOa 


CuO 


HgsO 


HgO 


AgC 


PtCbSbOi 




2 


2 


2 


2 3 


2 


2 


2 


2 


2 




2 


s 


2 


2 






2 




3 


3 






2 


CI 


1 


1 2 


1 


1 


] 


1 


2 


1 


3 




1 


I 


1 


2 


2 


1 






2 


2 


3 






S03 


1 


2 


1 




1 


1 


12 


1 


1 2 


1 


2 


N05 


1 


1 






1 


1 


1 


1 


1 


1 




POs 


2 


2 








2 


2 


2 









CO2 


2 


2 






2 


2 


2 


2 


2 






C2O3 


2 


2 


2 


1 


2 


2 


2 


2 


2 




12 


BOb 


2 


2 


2 




2 


2 


1 










A 


1 


1 


1 


1 


1 


1 


1 2 


1 


1 




1 


T 


2 


2 


i2 




2 


1 


i2 


2 


2 




1 


AsOd 




2 






2 


2 


2 


2 


2 




2 


AsOa 




2 








2 


2 


2 


2 




2 


CrO 


1 


2 


2 




2 


2 


2 


i2 


2 




2 



with both, contains the desired information. The numeral 
1, indicates solubility in water ; 2, solubility in either nitric 
or hydrochloric acid, and 3, insolubility in either. The 
smaller numerals indicate a low degree of solubility. 



464 



APPENDIX. 



TABLE XV. 

HOMOLOGOUS SERIES OF ORGANIC ACIDS. 



1. Formic . . . 


. C2H2O4 


16. Ethalic . . 


. . C32H32O4 


2. Acetic . . . 


. CtlLOi 


17. Stearic . . 


. . C31H3404 


3. Propionic . . 


. OsHsOi 


18. Bassic . . 


. . C36H3.04 


4. Butyric . . . 


. CsHsOi 


19. 




5. Valeric . . 


. . C10H11O4 


20. 




6. Caproic . . 


. . C12H1SO4 


21. 




7. Enanthylic . 


. CuHuCh 


22. Behenic 


. . C44H4404 


8. Caprylic . . 


. . C16H16O4 


23. 




9. Pelargonic . 


. CisHisOi 


24. 




10. Capric . . 


. C20H2CO1 


25. 




11. Margaritic . 


. . C22H22O4 


26. 




12. Laurie . . 


. C24H2104 


27. Cerotic . . 


. . C54H5404 


13. Cocinic . . 


. C25H2504 


28. 




14. Myristic . . . 


. C23H2S04 


29. 




15. Benic . . 




30. Melissic . . 


. . C60H6CO4 



TABLE XVI. 



COMPOSITION OF THE ASHES OF COMMON CROPS. 



r 


Indian 
Corn. 


Wheat 


Wheat 
Straw. 


Rye. 


Oats. 


Pota- 
toes. 


Tur- 
nips. 


Hay. 


Carbonic acid, 


trace. 










10*4 






Sulphuric acid, 


0-5 


l'O 


l-o 


1-5 


10-5 


7-1 


13.6 


2-7 


Phosphoric acid, 


49*2 


47'0 


3-1 


47-3 


43*8 


11-3 


7-6 


6-0 


Chlorine, . . 


0*3 


trace. 


0-6 




0-3 


2-7 


3-5 


2-6 


Lime, .... 


0-1 


2-9 


8'5 


2-9 


4-9 


1-8 


13-6 


22-9 


Magnesia, . . 


17-5 


15*9 


5'0 


10-1 


9-9 


5-4 


5*3 


5-7 


Potash, . . . 


23*2 


29-5 


7'2 


32-8 


I 27*2 


51-5 


42-0 


18-2 


Soda, .... 


3-8 


trace. 


0'3 


4'4 


trace. 


5-2 


2-3 


Silica, .... 


0-8 


1-3 


67*6 


0-2 


2-7 


8-6 


7-9 


37-9 


Iron, .... 


0.1 


trace. 


10 


0'8 


0*4 


0-5 


1-3 


1-7 


Charcoal in ash, ) 
and loss, . ) 


















4*5 


2-4 


5*7 




0*3 


0-7 








lOO'O 


100-0 


100*0 


lOO'O 


100*0 


lOO'O 


100-0 


lOO'O 


Lbs. of material J 












6000 


12500 


1000 


requir'd to yield >• 


10000 


5000 


2000 


5000 


2500 


to 


to 


to 


100 lbs. of ashes. ) 












13000 


20000 


2000 



INDEX. 



A. 

Acetic Acid, 372. 
Acid, Arsenious, 180, 

Antidote to, 185. 
Marsh's Test for, 181. 
Poisonous properties 
of, 181. 
Boracic, 197. 
Carbonic, 189. 
Hydrochloric, 210. 

Action of, on Metals, 
211. 
Hydrocyanic, 374. 
Hydrofluoric, 212. 
Hydrosulphuric, 214 
Muriatic, 210. 
Nitric, 173. 
Oxalic, 378. 
Prussic, 377, 
Stearic, 420. 
Sulphuric, 162. 
Sulphurous, 167. 
Stannic, 285. 
Tannic, 373. 
Acids, Formation of, 136. 
Organic, 372. 
Properties of, 137. 
Affinity, Relation of cohesion and, 

277. 
Air, Analysis of the, 172. 

Proportional Composition of 
the, 173. 



Unsaturated, 71. 
Albumen, Vegetable, 389. 
Alcohol, 362. 
Aldehyde, Conversion of Alcohol 

into, 370. 
Alkali, Volatile, 218. 
Alkalies, The, 286. 

Effects of, on "Wood, 35S. 

Vegetable, 395. 
Alkaloids, 
Alloys, 272 
Alum, 307. 

Different kinds of, 308. 
Alumina, 292. 
Aluminium, 238. 
Amalgams, 261. 
Ammonia, 21ft. 

Carbonate of, 315. 

Nitrate of, 311. 
Ammonium, 235. 

Oxide of, 290. 
Analysis, Chemical, 332. 

Organic, 430. 
Anastatic printing, 331. 
Animal Body, Chemical changes in 
the, 423. 

Heat, 423. 

Tissues, Changes of, 426. 
Antimony, 251. 

Apparatus for silvering and gild- 
ing, 107. 
Aqua Regia, 212. 
Arsenic, 179. 



21* 



4:66 



INDEX. 



Araenic, Eaters of Austria, 185. 

Marsh's Test for, 181. 
Artificial Essences, 382. 
Ashes, Effect of, on Soils, 407. 
Asphaltum, 386. 
Assay of Gold, 269. 

Silver, 265. 
Atmosphere, Elastic Force of the, 
78. 

Quantity of vapor in the, 71. 

Weight of the, 77. 
Atomic Weights, Table of, App. 
Atoms and Attraction, 1 1. 
Attraction, Chemical, 12. 

Distance of, 13. 

of Cohesion, 12. 

of Gravitation, 12. 



B. 

Barium, 237. 
Barometer Guage, 90. 
Baryta, Sulphate of, 307. 
Bases, Organic, 395. 

Properties of, 137. 
Batteries, Different kinds of, 114. 
Battery, Decomposition in the, 112. 
Bismuth, 253. 
Bleaching, by Oxygen, 147. 
Sulphur, 160. 

Powder, 298. 
Blood, Composition of the, 415. 

Changes in the, 423. 

Color of the, 424. 

Table of the Composition of 
the, App. 

Transformation of the, 413. 
Blowpipe, 227. 

Oxhydrogen, 229. 
Boiling, 77-80. 

Disappearance of Heat in, 81. 

Effect of Depth on, 83. 
Height on, 83. 

Expansion in, 81. 

Point, Artificial Change of, 84. 
Height measured by, 83. 
Bones, 415. 
Boracic Acid, 197. 
Borates, 323. 
Boron, 197. 



Bread, Raising of, 393. 
Bromine, 158. 
Burning Fluid, 380. 
Glasses, 46. 

of Ice, 47 



C. 

Calcium, 237. 

Ox ide of, 290. 
Camphors, 383. 
Caoutchouc, 387. 
Carbon, 185. 

Combustion of, 188. 
Carbonates, 313. 
Carbonic Acid, 189. 

Oxide, 194. 
Carburetted Hydrogen, Heavy,222. 
Light, 22 L. 
Casein, 389. 

Cellars warmed by Ice, 65. 
Cement, Hydraulic, 292. 
Chamelion Mineral, 326. 
Charcoal, Combustion of, in Oxy* 
gen, 145. 

Decoloring effects of, 188. 

Preparation of, 186-349. 

Preservative properties of, 187. 

Purifying properties of, 187. 

Reduction of Ores by, 188. 
Cheese, 423. 
Chemical Analysis, 332. 
Chemistry, Organic, General views 

of, 335. 
Chloride of Lime, 298. 

Sodium, 296. 
Chlorides, 294. 
Chlorine, 149. 

a Disinfectant, 154. 

Bleaching by, 153. 

Compounds of, with Oxygen. 
156. 

Relations to Animal Life, 155 

Resemblance to Oxygen, 155' 

Test for, 301. 
Chloroform, 371. 
Chromates, 325. 
Chromium, 245. 
Circulation of Matter, 432. 
Clay, 320. 



INDEX. 



467 



Cloth, Incombustible, 352. 
Coal, Anthracite, 351. 

Oils from, 355. 
Cobalt, 245. 
Cohesion, 12. 

Relation of, and Affinity, 277. 
Cold, Definition of, 27. 

Extreme, how measured, 59. 

Supposed Radiation of, 45. 

"Water, Lightness of, 55. 
Collodion, 356. 

Color, Change of, by Touch, 301. 
Coloring Matters, 396. 
Combustion, Definition of, 145. 

under Water, 178. 
Composts, 407. 
Compound Blowpipe, 229. 

Circuit, Decomposition by the, 
115. 

Galvanic Circuit, 114. 

Radicals, 340. 
Concave Lens, Action of, 22. 

Mirrors, Theory of, 19. 
Conducting Power, Simple Test 

of, 35. 
Copper, 254. 

Counterfeiting, Prevention of, 331. 
Crystal Forms, Systems of, 281. 

Glass, 321. 
Crj^stallization, 208. 
Culinary Paradox, 84. 
Cupellation, 263. 
Cyanides, 374. 
Cyanogen, 374. 



IK 

Daguerreotype, The, 327. 
Davy's Safety Lamp, 222. 
Decay, Preventives of, 352. 
Definite Proportions, Law of, 134. 
Dew, 75. 

Absence of, on Polished Sur- 
faces, 45. 

Artificial prevention of, 44. 

Formation of, 44. 

Point, 74. 

how to find the, 74. 
Distillation, 97 



Dyeing, 397. 
Dyes, Mineral, 399. 



E. 

Earth, Cooling of the, 43. 
Earthen-ware, 322. 
Effervescent Drinks, 191. 
Elastic Force of Vapors, 89 
Electric Light, 111. 
Electricity and Magnetism, 99. 

Conduction of, 103. 

Decomposition of water by, 
105. 

Frictional, 102. 

Galvanic, 103. 

Quantity of, in Matter, 104. 

Theory of, 102. 
Electrodes, 103. 

Elements, Electrical Relations of 
138. 

Number of, 11. 

Table of, App. 
Empyreumatic Oils, 382. 
Enamel, 322. 
Engine, The Steam, 91. 
Equivalents, Chemical, 134 

Table of, App. 
Essences, Artificial, 382. 
Essentials Oils, 379. 
Etching on Glass, 213. 
Ether, Conversion of Alcohol into, 

368. 
Ethyl, Production of, 369. 
Evaporation, Economy in, 97. 

Effect of Wind on, 70. 

Freezing by, 68. 

Protection from Heat by, 68. 
Expansion, 50. 

Fracture of Glass Vessels by, 
53. 

Law of, for Gases, 57. 

Lifting Walls by, 52. 

of Cold Water by Cold, 54. 
Gases, 56. 
Liquids, 54-56. 
Solids, 51. 
Wood and Marble, 53. 



468 



INPEX. 



F. 

Fats, Composition of, 418. 

Separation of, in Oil, 418. 

Tallow and 
Lard, 420. 
Fermentation, 391. 
Ferroc yan ides, 376. 
Fibre, Woody, 349. 
Filtration, 207. 
Fire by Compression, 50. 

on Water, 36. 

Proof Safes, 35. 
Flame, 225. 

Effect of, on Metals, 226. 
Flesh, 417. 
Fluorides, 302. 
Fluorine, 158. 
Fogs, 72. 

Food and Temperature, Relations 
of, 425. 

Proportions of, 428. 

Transformation of the, 413. 

Varieties of, 428. 
Freezing, 64. 

by Evaporation, 68. 

Mixtures, 63. 
Fusel Oil, 372. 



G. 

Galvanic Coil, Motion of a sus- 
pended, 120. 
Polarity of, imparted to 

Metals. 122. 
Polarity of the, 119. 
The, a magnetic needle, 
121. 
Coils, Mutual Action of, 121. 
Current, Heating Effects of 
the, 111. 
Magnetic Effects of the, 
119. 
Galvanism, Discovery of, 127. 

Physiological Effects of, 126. 
Gas from Wood, 225. 

Illuminating, £23-349. 
Gastric Juice, The, 413. 
Gelatine, 417. 



Germination, 345. 
Gilding, 270. 

Galvanic, 107. 
Glass, Colored, 322. 

Crystal, 321. 

cut by Hot Wire, 53. 

Etching on, 213. 

Soluble, 320. 

Staining, 294. 

Window, 320. 
Glauber's Salt, 306. 
Glycerine, 419. 
Gold, 267. 
Gravitation, 12. 
Green, Chrome, 326. 

Mineral, 400. 
Guano, 407. 
Gum from Wood, 357. 

Resins, 387. 
Gun Cotton, 355. 
Gunpowder, 311. 
Gutta Percha, 388. 
Gypsum, 305. 



II. 

Heat, Absorption of, 42. 

Analysis of, 46. 

Animal, 423. 

Capacity for, 49. 

Changes effected by, 48, 

Communication of, 30. 

Conduction of, 30. 

Convection of, 37. 

Disappearance of, in Boiling, 
81. 

Melting, 62. 
Yapors, 67. 

Extreme, how measured, 60. 

Latent, 65. 

Nature of, 25. 

of Chemical Action and Elec- 
tricity, 29. 
the Fixed Stars, 29. 

Protection from, by evapora- 
tion, 68. 

Quantity of, given out by tha 
Sun, 28. 

Radiation of, 89. 



INDEX. 



469 



Heat, Rays of, 45. 

Effect of different, 47. 
Reflection of, 41. 
Refraction of, 45. 
Relation of, to Density, 49. 
Specific, 48. 

the Ocean a Reservoir of, 50. 
Theories of, 25. 
Transmission of, 41. 
Heavy Carburetted Hydrogen, 

222. 
Hides, Tanning, 417. 
Homologous Series, 341. 

Table of the, of 
Organic Acids, 
App. 
Humus, Production of, 351. 
Hydrates, 286. 
Hydraulic Cement, 292. 
Hydrochloric Acid, 210. 
Hydrocyanic Acid, 374. 
Hydrofluoric Acid, 212. 
Hydrogen, 197. 

Phosphuretted, 219. 
Sulphuretted, 214. 



I. 

Ice in the Tropics, 43. 
Ignition by Lime, 291. 
Illuminating Gas, 223. 
Incrustations in Boilers, 316. 
Indigo, 396. 

Induction, Magnetic, without Con- 
tact, 101. 
Ink, Writing, 373. 
Intensity of Electricity, Meaning 

of, 115 
Iodine, 156. 
Iron, 240. 

Combustion of, in Oxygen, 143. 
Isomorphism, 284. 



Ii. 

Lamp Black, Preparation of, 187. 
Latent Heat, Proof that Boiling is 
effected bv, 96. 



Latent Heat, Quantity of, in Steam, 
96. 
Sum of, and Sensible Heat 
always the same, 96. 
Laughing Gas, 311. 
Lead, 256. 

Chromate of, 325. 
Light, 15. 

Analysis of, 22. 

Chemical Action of, 15-329. 

Laws of, 17. 

Medium, Definition of, 17. 

Ray, Definition of, 17. 

Reflection of, 18. 

Refraction of, 20. 

Theories of, 15. 
Light Carburetted Hydrogen, 221. 
Lime, Action of, in Soils, 405. 

Ignition by, 291. 

Nitrate of, 309. 

Sulphate of, 305. 
Liniments, 421. 
Liquefaction, 61. 

Liquids, Conversion of vapors into, 
95. 

Nonconductors of Heat, 36. 
Logwood, 397. 

Dyeing with, 399. 
Lunar Caustic, 312. 

m. 

Madder, 397. 
Magnesium. 237. 
Magnet, Artificial, 99. 
Magnetic Induction without Con- 
tact, 101. 

Needle, 99. 

Telegraph, 124. 
Magnets, Attraction of, for each 
other, 100. 

Native, 99. 
Magnetism, Electrical Theory of, 
126. 

Induced, 100. 
Mahomet's Coffin, 119. 
Manganates, 326. 
Manganese, 239. 
Marble, Artificial, 317. 
Marsh's Test for Arsenic, 181. 



470 



INDEX. 



Matches, Friction, 178. 
Mercury, 259. 

Quantity of, the Air can Sus- 
tain, 80. 
Metals, 231. 

Classification of, 231. 
Deposition of, by Electricity, 

106. 
Effect of flame on, 106. 
Milk, 421. 

Solid, 422. 

Table of the Composition of, 
Cow's, App. 
Human, App. 
Mineral Dyes, 399. 
Moisture, Deposition of, 70. 
Molasses, 361. 
Mordants, 398. 

Multiple Proportions, Laws of, 134. 
Muriatic Acid, 210. 

Effect of, on Wood, 354. 



W. 

Nickel, 246. 
Nitrate of Silver, 312. 
Nitrates, 309. 
Nitre, 310. 
Nitric Acid, 173. 

Effects of, on Wood, 352. 
Nitrogen, 169. 
Nutrition, Vegetable, 346. 



O. 

Oil of Vitriol, Manufacture of, 163. 
Oils, Empyreumatic, 382. 

Essential, 379. 

from Coal, 355. 
Olefiant Gas, Conversion of Alco- 
hol into, 369. 
Organic Acids, 372. 

Analysis, 429. 

Bases, 395. 

Chemistry, General Views of, 
335. 
Oxalic Acid, 378. 
Oxides, 285. 



Oxides, Formation of, 136. 

Names of, 135. 

reduced by Carbonic Oxide, 
195. 

Uses of, 293. 
Oxygen, 141. 

a Purveyor for Plants, 147. 

Bleaching by, 147. 

Compounds of, with Chlorine, 
156. 
Oxhydrogen Blowpipe, 229. 
Ozone, 148. 



P. 

Peat, 350. 
Petroleum, 386. 
Phosphates,. 317. 
Phosphorescence, 177. 
Phosphorus, 176. 

Combustion of, by Nitric Acid, 
176. 

Combustion of, in Oxygen, 144. 
Phosphuretted Hydrogen, 219. 
Photographs, 329. 
Plants, Constituents of, 348. 

Relation of, to the Soil, 402. 
Plaster, Aluminated, 306. 

of Paris, 305. 
Platinum, 271. 
Porcelain Painting, 323. 
Potassa, 287. 

Carbonate of, 314. 

Nitrate of, 310. 
Potassium, 233. 

Cyanide of, 375. 
Precipitation, 207-275. 
Pressure, Actual, in different En 
gines, 90. 

of the Atmosphere, 79. 

The Exact Relation of Temper- 
ature to, 88. 
Printing, Anastatic, 331. 

Calico, 400. 
Prism, construction of, 21. 

Effect of, on Rays, 21. 
Prussic Acid, 377. 
Putrefaction, 390. 



INDEX. 



471 



Quantity of Electricity, Meaning 
of, 115. 



R. 

Radiation of Heat, 39. 

Color not effected by, 40. 

Polish unfavorable to, 40. 

Proportion of, to Temperature, 
39. 
Radicals, Compound, 340. 
Rays, Heat and Chemical, 45. 
Refraction of Heat, 45. 
Light, 20. 
Refrigerators, Construction of, 34. 
Resins, 383. 

Gum, 387. 
Respiration, 424. 
Roots, Office of the, 347. 
Rosin Oil, 386. 

Soap, 385. 



S. 

Safety Lamp, Davy's, 222. 
Sal-Ammoniac, 218. 

Volatile, 315. 
Salt, Common, 296. 

Decomposition of a, by Gal- 
vanism, 117. 

Glauber's, 306. 
Saltpetre, 310. 
Salts, 274. 

Formation of, 136. 

Names of, 135. 
Sealing Wax, 385. 
Shot, Manufacture of, 259. 
Silicates, 319. 
Silicon, 196. 
Silver, 262. 

Assay, 265. 

Nitrate of, 312. 

obtained from Lead, 263. 
Silvering, Galvanic, 107. 
Sizing for Paper, 375. 
Skin, Tendons and Ligiments, 416. 



Soaps, 420. 

Properties of, 421. 
Soda, Carbonate of, 314. 

Sulphate of, 306. 
Sodium, 235. 

Chloride of, 296. 
Soils, 402. 
Soldering, 324. 
Soluble Glass, 320. 
Solution, 206-274. 

Effect of, on Chemical Affinity, 
138. 
Spirituous Liquors, 366. 
Stalactites, 317. 
Stalagmites, 317. 
Starch, 357. 
Starvation, 426. 
Steam Boilers, 86. 

Elastic Force of, 87. 

Engine, 91. 

Gu ages, 90. 

Heating Houses by, 95. 

Safety Valve, 91. 

Water Heated by, 95. 
Stearic Acid. 419. 
Steel, 243. 

Permanent Magnetism of, 123. 

Tempering, 244. 
Strontium, 237. 
Substitution, Equivalent, 339. 
Substitutions, 343. 
Sugar, Boiling in Vacuo, 85. 

Cane, 360. 

Grape, 359. 

from Starch, 358. 
Wood, 356. 

Manufacturing, Use of Sul- 
phurous Acid 
in, 159. 
Sulphates, 305. 
Sulphur, 159. 

Liver of, 303. 

Milk of, 304. 
Sulphurets, 302. 
Sulphuretted Hydrogen, 214. 
Sulphuric Acid, 162. 

Effect of, on Wood,,352. 
Sulphurous Acid, 167. 
Superphosphate of lime, 318-411 



472 



INDEX. 



Symbols, Calculation of Weights 
from, 133. 
Explanation of, 132. 



T. 

Tannic Acid, 373. 
Tanning, Hides, 418. 
Tar, Wood, 353. 
Tartar, 367. 

Tea Kettle, Singing of the, 86. 
Temperature and Food, Relations 
of, 426. 

Equilibrium of, 42. 

The exact Relation of Pres- 
sure to, 88. 
Thermometers, Graduation of, 58. 

Manufacture of, 57. 

The Air, 60. 
Tin, 248. 

Tissues, Repair of the, 428. 
Types, Chemical, 339. 



V. 

Vaporization, 66. 

Vapor, Capacity of the Air for, 75. 
. Quantity of, in the Atmos- 
phere, 69. 
Quantity of water the Air 

may contain as, 69. 
Relations of Air and, 69. 
Vapors, Conversion of Liquids in- 
to, 95. 
Density of, 66. 

depends on Tem- 
perature, 67. 
Elasticity of, 66. 
Formation of, 66. 
Transparent, 66. 
Varnishes, 384. 
Vegetable Chemistry, 345. 
Vinegar, Conversion of Alcohol 
into, 370. 
Process of Manufacture, 371. 
Wood, 353. 



Voltaic Pile, 118. 
Vulcanized Rubber, 387. 



W. 



Water, Action of, on Lead, 257. 
Affinity of Potassa for, 288. 
Capacity of Air for, increased 

by Heat, 70. 
Chemical Combinations of, 

208. 
Decomposition of, by Electri- 
city, 105-115. 
Hammer, 85. 
heated by Steam, 95. 
Proof of the Composition of, 

203-204. 
Quantity of, the Air may con- 
tain as Vapor, 69. 
Quantity of, the Pressure of 
the Air will Sustain, 
79. 
Sea, 297. 

Theory of the Decomposition 
of, 105. 
Welding Iron, 243. 
White Rotten Wood, 351. 
Window Glass, 320. 
Wines, 366. 
Wood, 349. 

Charred by Sulphuric Acid, 

167. 
Conversion into Gum, 357. 
Sugar, 356. 



Y. 

Yeast, 391. 

Powders, 393. 
Yellow, Chrome, 325-400, 



Z. 



Zinc, 246. 



APPARATUS AND MATERIALS. 473 



LIST OP CHEMICALS AND APPARATUS REQUIRED FOR THE EX- 
PERIMENTS DESCRIBED IN THIS WORK. 

1 lb. Black Oxide of Manganese - 
J " Bleaching Powders. 

J " Chlorate of Potassa. - 

\ « Alum. 

\ " Sulphur. - 

\ " Common Caustic Potash, in Sticks. 

\ " Acetate of Lead, (Sugar of Lead.) - 

\ " Sulphate of Copper, (Blue Vitriol.) 

\ " Carbonate of Ammonia, (Sal Volatile.) - 

2 oz. Bichromate of Potash. - 
2 " Bone Black. | 

2 " Sulphuret of Iron. - 

2 " Nitrate of Potash, (Salt Petre.) - 

1 " Chloride of Ammonium, (Sal Ammoniac.^ 

1 M Yellow Prussiate of Potash. L 

1 " Cyanide of Potassium. — 

1 u Oxalic Acid. 

1 " Ground Nut Galls. 

1 " Phosphorus. 

1 " Fluor Spar. 

] " Borax. 

1 " Chloride of Barium. 

1 " Chloride of Strontium. 

1 " Chloride of Mercury, (Corrosive Sublimate.) 

1 " Beeswax. 

1 " Metallic Antimony \ 

1 " Block Tin. 

1 u Bismuth. — 

2 " Mercury, (Quicksilver.) 

1 " Arsenious Acid, (Ratsbane.) 



474 APPARATUS AND MATERIALS. 

£ oz. Tartar Emetic. ~ 

J " Iodide of Potassium. - 

£ " Iodine. 

J M Potassium." 

J " Solution of Chloride of Platinum, 

1 Glass, (4 oz.) Spirit Lamp.^ 

Fine platinum foil and wire.- 

1 doz. assorted test-tubes. 

i sheet blue Litmus Paper, 

$ " red Litmus Paper. 

Fine Iron Wire. 

* Sheet Zinc. 

* Sheet Copper. 

* Sulphuric Acid, (Oil of Vitriol.) 

* Hydrochloric Acid, (Muriatic Acid.) 

* Nitric Acid, (aqua fortis.) 

* Alcohol. 

* Ethei 

* Clay Pipes and Vials. 

* Bowls, Tumblers, &c. 

* Not contained in the box of apparatus and materials put- up to 
accompany this work. 



APPENDIX. 455 

The latter constituent is, however, of comparatively little 
importance. The farmer who purchases his artificial fer- 
tilizers without a skillful and well attested analysis, is at the 
mercy of the ignorant or unscrupulous dealer. 

§ 1 046. Glycerine = C e H 8 O e . 

'Stearic Acid^CesHeeOe, 2HO=St, 2HO. 
§1047.«{Margaric Acid^C^HssOs, HO. 
Oleic Acid^CseHssOs, HO. 

(Urea=C 2 N2H40 2 . 
§1060, 1 Uric Acid=CioN 4 H 3 5 +HO. 

§ 1061. The view long entertained of the production of 
urea in the blood by the oxidation of the effete tissues has 
recently been confirmed by the artificial production of this 
substance from gluten, albumen and fibrine by a process of 
oxidation. 



30 



4:56 



APPENDIX. 



TABLE L 



TABLE OF THE DISOOVJCRY OF CERTAIN ELEMENTS. 



Names of Elements. 

Gold, . 

Silver, 

Iron, 

Copper, . 

Mercury, 

Lead, 

Tin,. . 

Sulphur, 

Carbon, 

Antimony 

Bismuth, 

Zinc, . . 

Phosphorus 

Arsenic, . 

Cobalt, . 

Hydrogen, 

Chlorine, 

Oxygen, . 

Manganese, 

Chromium, 

Potassium, 

Sodium, . 

Barium, . 

Strontium, 

Calcium, . 

Boron, . 

Iodine, , . 

Silicon, . 

Bromine, . 

Aluminium, 

Magnesium, 



Authors of the discovery. Dates. 



Known to the ancients. 



Described by Basil Valentine, 1490 

Described by Agricola, 1530 

First noted by Paracelsus, .... 16th century. 

Brand, 1660 

Brant, . . 1733 

Cavandish, 1766 

Scheele, 1774 

Priestly, 1774 

Gahn and Scheele, 1774 

Vauquelin, 1797 

Sir Humphrey Davy, 1807 

Courtois, 1811 

Berzelius, 1823 

Ballard, 1826 

Wohler, 1828 

Bussy, 1829 



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